12.2: Intellectual Property
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- Ly-Huong T. Pham, Tejal Desai-Naik, Laurie Hammond, & Wael Abdeljabbar
- ASCCC Open Educational Resources Initiative (OERI)
Intellectual Property
One of the domains that digital technologies have deeply impacted is the domain of intellectual property. Digital technologies have driven a rise in new intellectual property claims and made it much more difficult to defend intellectual property.
Merriam-Webster Dictionary defines Intellectual property as “property (as an idea, invention, or process) that derives from the work of the mind or intellect. This could include song lyrics, a computer program, a new type of toaster, or even a sculpture.
Practically speaking, it is challenging to protect an idea. Instead, intellectual property laws are written to protect the tangible results of an idea. In other words, just coming up with a song in your head is not protected, but if you write it down, it can be protected.
Protection of intellectual property is important because it gives people an incentive to be creative. Innovators with great ideas will be more likely to pursue those ideas if they clearly understand how they will benefit. In the US Constitution, Article 8, Section 8, the authors saw fit to recognize the importance of protecting creative works:
Congress shall have the power... To promote the Progress of Science and useful Arts by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.
An important point to note here is the “limited time” qualification. While protecting intellectual property is important because of its incentives, it is also necessary to limit the amount of benefit that can be received and allow the results of ideas to become part of the public domain.
Outside of the US, intellectual property protections vary. You can find out more about a specific country’s intellectual property laws by visiting the World Intellectual Property Organization .
There are many intellectual property types such as copyrights, patents, trademarks, industrial design rights, plant variety rights, and trade secrets. In the following sections, we will review three of the best-known intellectual property protection: copyright, patent, and trademark.
Copyright
Copyright is the protection given to songs, movies, books, computer software, architecture, and other creative works, usually for a limited time. An artist can, for example, sue if his painting is copied and sold on T-shirts without permission. A coder can sue if another Web developer verbatim takes her code. Any work that has an “author” can be copyrighted. It covers both published and unpublished work. Under the terms of copyright, the author of the work controls what can be done with the work, including:
- Who can make copies of the work?
- Who can create derivative works from the original work?
- Who can perform the work publicly?
- Who can display the work publicly?
- Who can distribute the work?
Often, work is not owned by an individual but is instead owned by a publisher with whom the original author has an agreement. In return for the rights to the work, the publisher will market and distribute the work and then pay the original author a portion of the proceeds.
Copyright protection lasts for the life of the original author plus seventy years. In the case of a copyrighted work owned by a publisher or another third party, the protection lasts for ninety-five years from the original creation date. For works created before 1978, the protections vary slightly. You can see the full details on copyright protections by reviewing the Copyright Basics document available at the US Copyright Office’s website . See also the sidebar “History of Copyright Law.”
Obtaining Copyright Protection
In the United States, copyright is obtained by the simple act of creating the original work. In other words, when an author writes down that song, makes that film, or designs that program, he or she automatically has the copyright. However, it is advisable to register for a copyright with the US Copyright Office for a work that will be used commercially. A registered copyright is needed to bring legal action against someone who has used a work without permission.
First Sale Doctrine
If an artist creates a painting and sells it to a collector who then, for whatever reason, proceeds to destroy it, does the original artist have any recourse? What if the collector, instead of destroying it, begins making copies of it and sells them? Is this allowed?
The protections that copyright law extends to creators have an important limitation. The first sale doctrine is a part of copyright law that addresses this, as shown below :
The first sale doctrine, codified at 17 U.S.C. § 109, provides that an individual who knowingly purchases a copy of a copyrighted work from the copyright holder receives the right to sell, display or otherwise dispose of that particular copy, notwithstanding the interests of the copyright owner.
So, in our examples, the copyright owner has no recourse if the collector destroys her artwork. But the collector does not have the right to make copies of the artwork.
Fair Use
Another important provision within copyright law is that of fair use. Fair use is a limitation on copyright law that allows for protected works without prior authorization in specific cases. For example, if a teacher wanted to discuss a current event in her class, she could pass out copies of a copyrighted news story to her students without first getting permission. Fair use allows a student to quote a small portion of a copyrighted work in a research paper.
Unfortunately, the specific guidelines for what is considered fair use and what constitutes copyright violation are not well defined. Fair use is a well-known and respected concept and will only be challenged when copyright holders feel that their work's integrity or market value is being threatened. The following four factors are considered when determining if something constitutes fair use 9 :
- The purpose and character of the use, including whether such use is of commercial nature or is for nonprofit educational purposes;
- The nature of the copyrighted work;
- The amount and substantiality of the portion used concerning the copyrighted work as a whole;
- The effect of the use upon the potential market for, or value of, the copyrighted work.
If you are ever considering using a copyrighted work as part of something you are creating, you may be able to do so under fair use. However, it is always best to check with the copyright owner to ensure you are staying within your rights and not infringing upon theirs.
Sidebar: The History of Copyright Law
As noted above, current copyright law grants copyright protection for seventy years after the author’s death or ninety-five years from the date of creation for a work created for hire. But it was not always this way.
The first US copyright law, which only protected books, maps, and charts, protected for only 14 years with a renewable term of 14 years. Over time, copyright law was revised to grant protections to other forms of creative expressions, such as photography and motion pictures. Congress also saw fit to extend the length of the protections, as shown in the chart below. Today, copyright has become big business, with many businesses relying on copyright-protected works for their income.
Many now think that the protections last too long. The Sonny Bono Copyright Term Extension Act 1998 has been nicknamed the “Mickey Mouse Protection Act,” as it was enacted just in time to protect the copyright on the Walt Disney Company’s Mickey Mouse character. It extended copyright terms to the life of the author plus 70 years. Because of this term extension, many works from the 1920s and 1930s were still protected by copyright and could not enter the public domain until 2019 or later. Mickey Mouse will not be in the public domain until 2024.
References
ACM Code of Ethics. Preamble . Retrieved November 10, 2020, from https://www.acm.org/code-of-ethics .
US copyright. Copyright basics . Retrieved November 10, 2020, from https://www.copyright.gov/ .
US copyright. More information on fair use . Retrieved from https://www.copyright.gov/fair-use/more-info.html .


1: Observation and Documentation - The Key to Intentional Teaching
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To provide children with a safe and nurturing learning environment and to maintain program effectiveness, teachers must incorporate observation, documentation and assessment into their daily routines. To truly be effective, teachers must develop skills and strategies that are grounded in
best practices.
In this chapter you will be presented with information that highlights how observation and documentation can be used as a key strategy to ensure intentional teaching. You will examine the initial steps to take to becoming a skilled observer, and you will reflect on how to objectively document the interactions that you see and the conversations that you hear. It is important to note that becoming a skilled observer takes time and practice, and that learning how to incorporate observation, documentation and assessment into your regular routines and daily duties requires some thoughtful consideration.
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1.1: The Role of Observation
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Observations in early childhood classrooms are essential for ensuring safety, assessing health, and maintaining a conducive learning environment. Teachers use observations to plan curricula, monitor social interactions, communicate with families, and track child development. Observations provide insights into a child's personality, problem-solving skills, and cultural practices. They help teachers evaluate effectiveness, implement improvements, and support diverse needs.
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1.2: Becoming a Skilled Observer
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To effectively observe a child, one needs to be present, knowledgeable, inquisitive, and intentional. Being present allows you to capture subtle nuances and details, while being knowledgeable helps set realistic expectations based on early childhood education principles. Being inquisitive involves conducting research by asking thoughtful questions, and being intentional requires a thoughtful plan of action, ensuring that every interaction has a specific goal and purpose.
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1.3: Observations can be Spontaneous or Planned
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Spontaneous observations occur all the time. Whether teachers are actively engaged with their children during an activity or in the background cleaning up after an activity, teachers have numerous opportunities to see and hear some wonderful developments as they randomly occur. Planned observations require becoming a skilled observer and takes practice. At first you may be slightly overwhelmed with trying to incorporate an official observation time into your already busy schedule.
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1.4: Questions you may want to ask yourself as you plan your next observation
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The text discusses the importance and methodology of observing children in classroom settings to understand their full potential and development. Observations should occur at various times and in different environments to capture a comprehensive view of a child's abilities and social interactions. It highlights the need for utilizing multiple observation methods and maintaining an open, unbiased perspective while observing each child as an individual and within group dynamics.
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1.5: The Role of Documentation
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A high-quality early care and education program prioritizes observing, documenting, and assessing children's development to guide classroom activities. Effective documentation involves using various methods such as running records, anecdotes, checklists, and portfolios to collect and store data. Each child's portfolio should contain observations across developmental domains to build a comprehensive picture of their growth.
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1.6: Objective versus Subjective Observation Evidence
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The importance of writing objective observations is highlighted for intentional teachers, emphasizing the distinction between objective and subjective observations. Objective observations focus on recording facts based on the senses without bias, while subjective observations may include personal opinions and cultural biases. Tips for crafting objective observations include reporting only what is seen or heard and avoiding subjective language.
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1.7: Recognizing Your Biases
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The text explores the concept of bias, explaining that biases are inherent in everyone due to their upbringing and experiences and significantly affect beliefs, attitudes, and behavior. It emphasizes the importance of recognizing and understanding personal biases, particularly in educational settings, to avoid unfair treatment based on preconceived notions. Teachers are encouraged to observe and reflect objectively, avoiding common pitfalls such as making assumptions or labeling behaviors.
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1.8: Ethical Guidelines when Observing Children
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In observing and documenting children's development, teachers must consider ethical implications, particularly regarding the child's rights and privacy. Balancing documentation with engagement and ensuring children's comfort and consent is vital. Guidelines stress the importance of confidentiality, respecting children's preferences, being non-intrusive, and avoiding cultural biases.
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1.9: Observation and Documentation Dos and Don’ts
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When conducting observations, whether planned or spontaneous, it's important to ensure quality evidence is recorded. Key do's include noting precise details like date, time, setting, and using varied observation methods. Observe facts objectively, and focus on what children can do, while maintaining an unobtrusive presence. Don't interfere, assume, use biased language, or summarize. Refrain from labeling and stick to factual, unbiased descriptions.
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1.10: Conclusion and References
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Becoming a skilled observer in an educational context requires time and practice to incorporate observation and documentation into a regular routine. Intentional teachers should plan systematic observations to document each child???s unique qualities, interests, developmental strengths, and cultural practices. Gathering evidence objectively while recognizing biases is crucial. Documentation should be organized chronologically and stored securely, ensuring all children are observed consistently.


3.3.1: The Perceptual Process
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exploring perceptions affect workplace harmony
Personal Perceptions Affect Workplace Harmony
Conflict was a feeling that James and Chaz were familiar with in their workplace. It was just a matter of time before their differences bubbled up to form a real hardship on themselves as well as their management teams.
Chaz is anxious to get ahead, really focused on how fast he can accelerate his career. In order to showcase his tenacity, he stays extra hours and often takes on extra assignments from upper management and doesn’t seem to mind. James, on the other hand, is content in his position and believes that if he does his regular job, he will be seen a stable part of the team and will be rewarded for his everyday efforts. James views Chaz’s behavior as “kissing up” and resents Chaz for his extra efforts because it may make his own work look bad. James doesn’t give a thought to the personal reasons why Chaz may be acting that way, and instead ends up treating Chaz poorly, with a short temper every time they have to work together.
Chaz talks to his manager, Jerry, about the way that he is being treated by James. He explains that he has been having some personal troubles at home, his wife is expecting, and they are trying to save for the new addition to their family. Chaz is feeling pressure to work hard and showcase his talents in order to get a raise. He also expresses his feelings against James, mainly that he shouldn’t be scrutinized for going above and beyond when his colleagues may just decide to do the minimum requirements.  They talk about ways to measure Chaz’s extra efforts and plan a conversation during their annual review period to discuss his raise again. Jerry also suggests that Chaz talk with James to alleviate some of the negative behavior he is experiencing. He feels that if James understood the reasons behind Chaz’s actions, he may be less jealous and feel less threatened by him.
Questions:
- How can an individual’s perceptions be a challenge in the workplace?
- What can James do in the future to address Chaz in a different manner and better understand his actions?
- What do you think Jerry could have done differently to help his employees overcome their differences and work more efficiently together?
1. How do differences in perception affect employee behavior and performance?
By
perception
, we mean the process by which one screen, selects, organizes, and interprets stimuli to give them meaning.
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It is a process of making sense out of the environment in order to make an appropriate behavioral response. Perception does not necessarily lead to an accurate portrait of the environment, but rather to a unique portrait, influenced by the needs, desires, values, and disposition of the perceiver. As described by Kretch and associates.
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an individual's perception of a given situation is not a photographic representation of the physical world; it is a partial, personal construction in which certain objects, selected by the individual for a major role, are perceived in an individual manner. Every perceiver is, as it were, to some degree a nonrepresentational artist, painting a picture of the world that expresses an individual view of reality.
The multitude of objects that vie for attention are first selected or screened by individuals. This process is called perceptual selectivity . Certain of these objects catch our attention, while others do not. Once individuals notice a particular object, they then attempt to make sense out of it by organizing or categorizing it according to their unique frame of reference and their needs. This second process is termed perceptual organization . When meaning has been attached to an object, individuals are in a position to determine an appropriate response or reaction to it. Hence, if we clearly recognize and understand we are in danger from a falling rock or a car, we can quickly move out of the way.
Because of the importance of perceptual selectivity for understanding the perception of work situations, we will examine this concept in some detail before considering the topic of social perception.
Perceptual Selectivity: Seeing What We See
As noted above, perceptual selectivity refers to the process by which individuals select objects in the environment for attention. Without this ability to focus on one or a few stimuli instead of the hundreds constantly surrounding us, we would be unable to process all the information necessary to initiate behavior. In essence, perceptual selectivity works as follows (see Exhibit 3.2 ). The individual is first exposed to an object or stimulus—a loud noise, a new car, a tall building, another person, and so on. Next, the individual focuses attention on this one object or stimulus, as opposed to others, and concentrates his efforts on understanding or comprehending the stimulus. For example, while conducting a factory tour, two managers came across a piece of machinery. One manager’s attention focused on the stopped machine; the other manager focused on the worker who was trying to fix it. Both managers simultaneously asked the worker a question. The first manager asked why the machine was stopped, and the second manager asked if the employee thought that he could fix it. Both managers were presented with the same situation, but they noticed different aspects. This example illustrates that once attention has been directed, individuals are more likely to retain an image of the object or stimulus in their memory and to select an appropriate response to the stimulus. These various influences on selective attention can be divided into external influences and internal (personal) influences (see Exhibit 3.3 ).
External Influences on Selective Attention
External influences consist of the characteristics of the observed object or person that activate the senses. Most external influences affect selective attention because of either their physical properties or their dynamic properties.
Physical Properties. The physical properties of the objects themselves often affect which objects receive attention by the perceiver. Emphasis here is on the unique, different, and out of the ordinary. A particularly important physical property is size . Generally, larger objects receive more attention than smaller ones. Advertising companies use the largest signs and billboards allowed to capture the perceiver’s attention. However, when most of the surrounding objects are large, a small object against a field of large objects may receive more attention. In either case, size represents an important variable in perception. Moreover, brighter, louder, and more colorful objects tend to attract more attention than objects of less intensity . For example, when a factory foreman yells an order at his subordinates, it will probably receive more notice (although it may not receive the desired response) from workers. It must be remembered here, however, that intensity heightens attention only when compared to other comparable stimuli. If the foreman always yells, employees may stop paying much attention to the yelling. Objects that contrast strongly with the background against which they are observed tend to receive more attention than less-contrasting objects. An example of the contrast principle can be seen in the use of plant and highway safety signs. A terse message such as “Danger” is lettered in black against a yellow or orange background. A final physical characteristic that can heighten perceptual awareness is the novelty or unfamiliarity of the object. Specifically, the unique or unexpected seen in a familiar setting (an executive of a conservative company who comes to work in Bermuda shorts) or the familiar seen in an incongruous setting (someone in church holding a can of beer) will receive attention.
Dynamic Properties. The second set of external influences on selective attention are those that either change over time or derive their uniqueness from the order in which they are presented. The most obvious dynamic property is motion . We tend to pay attention to objects that move against a relatively static background. This principle has long been recognized by advertisers, who often use signs with moving lights or moving objects to attract attention. In an organizational setting, a clear example is a rate-buster, who shows up his colleagues by working substantially faster, attracting more attention.
Another principle basic to advertising is repetition of a message or image. Work instructions that are repeated tend to be received better, particularly when they concern a dull or boring task on which it is difficult to concentrate. This process is particularly effective in the area of plant safety. Most industrial accidents occur because of careless mistakes during monotonous activities. Repeating safety rules and procedures can often help keep workers alert to the possibilities of accidents.
Personal Influences on Selective Attention
In addition to a variety of external factors, several important personal factors are also capable of influencing the extent to which an individual pays attention to a particular stimulus or object in the environment. The two most important personal influences on perceptual readiness are response salience and response disposition .
Response Salience. This is a tendency to focus on objects that relate to our immediate needs or wants. Response salience in the work environment is easily identified. A worker who is tired from many hours of work may be acutely sensitive to the number of hours or minutes until quitting time. Employees negotiating a new contract may know to the penny the hourly wage of workers doing similar jobs across town. Managers with a high need to achieve may be sensitive to opportunities for work achievement, success, and promotion. Finally, female managers may be more sensitive than many male managers to condescending male attitudes toward women. Response salience, in turn, can distort our view of our surroundings. For example, as Ruch notes:
“Time spent on monotonous work is usually overestimated. Time spent in interesting work is usually underestimated. . . . Judgment of time is related to feelings of success or failure. Subjects who are experiencing failure judge a given interval as longer than do subjects who are experiencing success. A given interval of time is also estimated as longer by subjects trying to get through a task in order to reach a desired goal than by subjects working without such motivation.” 3
Response Disposition. Whereas response salience deals with immediate needs and concerns, response disposition is the tendency to recognize familiar objects more quickly than unfamiliar ones. The notion of response disposition carries with it a clear recognition of the importance of past learning on what we perceive in the present. For instance, in one study, a group of individuals was presented with a set of playing cards with the colors and symbols reversed—that is, hearts and diamonds were printed in black, and spades and clubs in red. Surprisingly, when subjects were presented with these cards for brief time periods, individuals consistently described the cards as they expected them to be (red hearts and diamonds, black spades and clubs) instead of as they really were. They were predisposed to see things as they always had been in the past. 4
Thus, the basic perceptual process is in reality a fairly complicated one. Several factors, including our own personal makeup and the environment, influence how we interpret and respond to the events we focus on. Although the process itself may seem somewhat complicated, it in fact represents a shorthand to guide us in our everyday behavior. That is, without perceptual selectivity we would be immobilized by the millions of stimuli competing for our attention and action. The perceptual process allows us to focus our attention on the more salient events or objects and, in addition, allows us to categorize such events or objects so that they fit into our own conceptual map of the environment.
expanding around the globe
Which Car Would You Buy?
When General Motors teamed up with Toyota to form California-based New United Motor Manufacturing Inc. (NUMMI), they had a great idea. NUMMI would manufacture not only the popular Toyota Corolla but would also make a GM car called the Geo Prizm. Both cars would be essentially identical except for minor styling differences. Economies of scale and high quality would benefit the sales of both cars. Unfortunately, General Motors forgot one thing. The North American consumer holds a higher opinion of Japanese-built cars than American-made ones. As a result, from the start of the joint venture, Corollas have sold rapidly, while sales of Geo Prizms have languished.
With hindsight, it is easy to explain what happened in terms of perceptual differences. That is, the typical consumer simply perceived the Corolla to be of higher quality (and perhaps higher status) and bought accordingly. Not only was the Prizm seen more skeptically by consumers, but General Motors’ insistence on a whole new name for the product left many buyers unfamiliar with just what they were buying. Perception was that main reason for lagging sales; however, the paint job on the Prizm was viewed as being among the worst ever. As a result, General Motors lost $80 million on the Prizm in its first year of sales. Meanwhile, demand for the Corolla exceeded supply.
The final irony here is that no two cars could be any more alike than the Prizm and the Corolla. They are built on the same assembly line by the same workers to the same design specifications. They are, in fact, the same car. The only difference is in how the consumers perceive the two cars—and these perceptions obviously are radically different.
Over time, however, perceptions did change. While there was nothing unique about the Prizm, the vehicle managed to sell pretty well for the automaker and carried on well into the 2000s. The Prizm was also the base for the Pontiac Vibe, which was based on the Corolla platform as well, and this is one of the few collaborations that worked really well.
Sources: C. Eitreim, “10 Odd Automotive Brand Collaborations (And 15 That Worked),” Car Culture , January 19, 2019; R. Hof, “This Team-Up Has It All—Except Sales,” Business Week, August 14, 1989, p. 35; C. Eitreim, “15 GM Cars With The Worst Factory Paint Jobs (And 5 That'll Last Forever),” Motor Hub , November 8, 2018.
Social Perception in Organizations
Up to this point, we have focused on an examination of basic perceptual processes—how we see objects or attend to stimuli. Based on this discussion, we are now ready to examine a special case of the perceptual process— social perception as it relates to the workplace. Social perception consists of those processes by which we perceive other people. 5 Particular emphasis in the study of social perception is placed on how we interpret other people, how we categorize them, and how we form impressions of them.
Clearly, social perception is far more complex than the perception of inanimate objects such as tables, chairs, signs, and buildings. This is true for at least two reasons. First, people are obviously far more complex and dynamic than tables and chairs. More-careful attention must be paid in perceiving them so as not to miss important details. Second, an accurate perception of others is usually far more important to us personally than are our perceptions of inanimate objects. The consequences of misperceiving people are great. Failure to accurately perceive the location of a desk in a large room may mean we bump into it by mistake. Failure to perceive accurately the hierarchical status of someone and how the person cares about this status difference might lead you to inappropriately address the person by their first name or use slang in their presence and thereby significantly hurt your chances for promotion if that person is involved in such decisions. Consequently, social perception in the work situation deserves special attention.
We will concentrate now on the three major influences on social perception: the characteristics of (1) the person being perceived, (2) the particular situation, and (3) the perceiver. When taken together, these influences are the dimensions of the environment in which we view other people. It is important for students of management to understand the way in which they interact (see Exhibit 3.4 ).
The way in which we are evaluated in social situations is greatly influenced by our own unique sets of personal characteristics. That is, our dress, talk, and gestures determine the kind of impressions people form of us. In particular, four categories of personal characteristics can be identified: (1) physical appearance, (2) verbal communication, (3) nonverbal communication, and (4) ascribed attributes.
Physical Appearance. A variety of physical attributes influence our overall image. These include many of the obvious demographic characteristics such as age, sex, race, height, and weight. A study by Mason found that most people agree on the physical attributes of a leader (i.e., what leaders should look like), even though these attributes were not found to be consistently held by actual leaders. However, when we see a person who appears to be assertive, goal-oriented, confident, and articulate, we infer that this person is a natural leader. Another example of the powerful influence of physical appearance on perception is clothing. People dressed in business suits are generally thought to be professionals, whereas people dressed in work clothes are assumed to be lower-level employees.
Verbal and Nonverbal Communication. What we say to others—as well as how we say it—can influence the impressions others form of us. Several aspects of verbal communication can be noted. First, the precision with which one uses language can influence impressions about cultural sophistication or education. An accent provides clues about a person’s geographic and social background. The tone of voice used provides clues about a speaker’s state of mind. Finally, the topics people choose to converse about provide clues about them.
Impressions are also influenced by nonverbal communication—how people behave. For instance, facial expressions often serve as clues in forming impressions of others. People who consistently smile are often thought to have positive attitudes. 7 A whole field of study that has recently emerged is body language , the way in which people express their inner feelings subconsciously through physical actions: sitting up straight versus being relaxed, looking people straight in the eye versus looking away from people. These forms of expressive behavior provide information to the perceiver concerning how approachable others are, how self-confident they are, or how sociable they are.
Ascribed Attributes. Finally, we often ascribe certain attributes to a person before or at the beginning of an encounter; these attributes can influence how we perceive that person. Three ascribed attributes are status, occupation, and personal characteristics. We ascribe status to someone when we are told that he or she is an executive, holds the greatest sales record, or has in some way achieved unusual fame or wealth. Research has consistently shown that people attribute different motives to people they believe to be high or low in status, even when these people behave in an identical fashion. 8 For instance, high-status people are seen as having greater control over their behavior and as being more self-confident and competent; they are given greater influence in group decisions than low-status people. Moreover, high-status people are generally better liked than low-status people. Occupations also play an important part in how we perceive people. Describing people as salespersons, accountants, teamsters, or research scientists conjures up distinct pictures of these various people before any firsthand encounters. In fact, these pictures may even determine whether there can be an encounter.
Characteristics of the Situation
The second major influence on how we perceive others is the situation in which the perceptual process occurs. Two situational influences can be identified: (1) the organization and the employee’s place in it, and (2) the location of the event.
Organizational Role. An employee’s place in the organizational hierarchy can also influence his perceptions. A classic study of managers by Dearborn and Simon emphasizes this point. In this study, executives from various departments (accounting, sales, production) were asked to read a detailed and factual case about a steel company. 9 Next, each executive was asked to identify the major problem a new president of the company should address. The findings showed clearly that the executives’ perceptions of the most important problems in the company were influenced by the departments in which they worked. Sales executives saw sales as the biggest problem, whereas production executives cited production issues. Industrial relations and public relations executives identified human relations as the primary problem in need of attention.
In addition to perceptual differences emerging horizontally across departments, such differences can also be found when we move vertically up or down the hierarchy. The most obvious difference here is seen between managers and unions, where the former see profits, production, and sales as vital areas of concern for the company whereas the latter place much greater emphasis on wages, working conditions, and job security. Indeed, our views of managers and workers are clearly influenced by the group to which we belong. The positions we occupy in organizations can easily color how we view our work world and those in it. Consider the results of a classical study of perceptual differences between superiors and subordinates. 10 Both groups were asked how often the supervisor gave various forms of feedback to the employees. The results, shown in Table 3.1 , demonstrate striking differences based on one’s location in the organizational hierarchy.
Location of Event. Finally, how we interpret events is also influenced by where the event occurs. Behaviors that may be appropriate at home, such as taking off one’s shoes, may be inappropriate in the office. Acceptable customs vary from country to country. For instance, assertiveness may be a desirable trait for a sales representative in the United States, but it may be seen as being brash or coarse in Japan or China. Hence, the context in which the perceptual activity takes place is important.
Characteristics of the Perceiver
The third major influence on social perception is the personality and viewpoint of the perceiver. Several characteristics unique to our personalities can affect how we see others. These include (1) self-concept, (2) cognitive structure, (3) response salience, and (4) previous experience with the individual. 11
Self-Concept. Our self-concept represents a major influence on how we perceive others. This influence is manifested in several ways. First, when we understand ourselves (i.e., can accurately describe our own personal characteristics), we are better able to perceive others accurately. Second, when we accept ourselves (i.e., have a positive self-image), we are more likely to see favorable characteristics in others. Studies have shown that if we accept ourselves as we are, we broaden our view of others and are more likely to view people uncritically. Conversely, less secure people often find faults in others. Third, our own personal characteristics influence the characteristics we notice in others. For instance, people with authoritarian tendencies tend to view others in terms of power, whereas secure people tend to see others as warm rather than cold. 12 From a management standpoint, these findings emphasize how important it is for administrators to understand themselves; they also provide justification for the human relations training programs that are popular in many organizations today.
Cognitive Structure. Our cognitive structures also influence how we view people. People describe each other differently. Some use physical characteristics such as tall or short, whereas others use central descriptions such as deceitful, forceful, or meek. Still others have more complex cognitive structures and use multiple traits in their descriptions of others; hence, a person may be described as being aggressive, honest, friendly, and hardworking. (See the discussion in Individual and Cultural Differences on cognitive complexity.) Ostensibly, the greater our cognitive complexity—our ability to differentiate between people using multiple criteria—the more accurate our perception of others. People who tend to make more complex assessments of others also tend to be more positive in their appraisals.13 Research in this area highlights the importance of selective managers who exhibit high degrees of cognitive complexity. These individuals should form more accurate perceptions of the strengths and weaknesses of their subordinates and should be able to capitalize on their strengths while ignoring or working to overcome their weaknesses.
Response Salience. This refers to our sensitivity to objects in the environment as influenced by our particular needs or desires. Response salience can play an important role in social perception because we tend to see what we want to see. A company personnel manager who has a bias against women, minorities, or handicapped persons would tend to be adversely sensitive to them during an employment interview. This focus may cause the manager to look for other potentially negative traits in the candidate to confirm his biases. The influence of positive arbitrary biases is called the halo effect , whereas the influence of negative biases is often called the horn effect . Another personnel manager without these biases would be much less inclined to be influenced by these characteristics when viewing prospective job candidates.
Previous Experience with the Individual. Our previous experiences with others often will influence the way in which we view their current behavior. When an employee has consistently received poor performance evaluations, a marked improvement in performance may go unnoticed because the supervisor continues to think of the individual as a poor performer. Similarly, employees who begin their careers with several successes develop a reputation as fast-track individuals and may continue to rise in the organization long after their performance has leveled off or even declined. The impact of previous experience on present perceptions should be respected and studied by students of management. For instance, when a previously poor performer earnestly tries to perform better, it is important for this improvement to be recognized early and properly rewarded. Otherwise, employees may give up, feeling that nothing they do will make any difference.
Together, these factors determine the impressions we form of others (see Exhibit 3.4 ). With these impressions, we make conscious and unconscious decisions about how we intend to behave toward people. Our behavior toward others, in turn, influences the way they regard us. Consequently, the importance of understanding the perceptual process, as well as factors that contribute to it, is apparent for managers. A better understanding of ourselves and careful attention to others leads to more accurate perceptions and more appropriate actions.
concept check
1. How can you understand what makes up an individual’s personality?
2. How does the content of the situation affect the perception of the perceiver?
3. What are the characteristics that the perceiver can have on interpreting personality?
1. M. W. Levine and J. M. Shefner, Fundamentals of Selection and Perception (Reading, Mass.: Addison-Wesley, 1981).
2. D. Kretch, R. S. Crutchfield, and E. L. Ballachey, Individual in Society (New York: McGraw-Hill, 1962).
3. F. L. Ruch, Psychology and life (Glenview: Scott, Foresman, 1983).
4. J. S. Bruner and L. Postman, “On the Perception of Incongruity: A Paradigm,” Journal of Personality , 1949, 18, pp. 206–223.
5. S. T. Fiske and S. E. Taylor, Social Cognition (Reading, Mass.: Addison-Wesley, 1984).
6. D. J. Mason, “Judgements of Leadership Based on Physiognomic Cues,” Journal of Abnormal and Social Psychology , 1957, 54, pp. 273–274.
7. P. F. Secord, “The Role of Facial Features in Interpersonal Perception,” in R. Tagiuri and L. Petrullo, eds., Person Perception and Interpersonal Behavior (Palo Alto: Stanford University Press, 1958), pp. 300–315.
8. J. W. Thibaut and H. W. Riecker, “Authoritarianism, Status, and the Communication of Aggression,” Human Relations , 1955, 8, pp. 95–120.
9. D. C. Dearborn and H. A. Simon, “Selective Perception: A Note on Departmental Identification of Executives,” Sociometry, 1958, 21 , p. 142.
10. R. Likert, New Patterns of Management (New York: McGraw-Hill, 1961).
11. Levine and Shefner, op. cit.
12. Ibid.
13. K. J. Frauenfelder, “A Cognitive Determinant of Favorability of Impression,” Journal of Social Psychology, 1974, 94, pp. 71–81.
Table 3.1 (Attribution: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license)
Exhibit 3.2 The Process of Perceptual Selectivity (Attribution: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license)
Exhibit 3.3 Major Influences on Selective Attention (Attribution: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license)
Exhibit 3.4 Major Influences on Social Perception in Organizations (Attribution: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license)


Space
Very often, objects that are spatially close to us are more relevant than more distant objects. Therefore, one would expect the same for situation models. consistent with this idea, comprehenders are slower to recognise words denoting objects distant from a protagonist than those denoting objects close to the protagonist (Glenberg, Meyer & Lindem, 1987).
When comprehenders have extensive knowledge of the spatial layout of the setting of the story (e.g., a building), they update their representations according to the location and goals of the protagonist. They have the fastest mental access to the room that the protagonist is currently in or is heading to. For example, they can more readily say whether or not two objects are in the same room if the room mentioned is one of these rooms than if it is some other room in the building (e.g., Morrow, Greenspan, & Bower, 1987). This makes perfect sense intuitively because these are the rooms that would be relevant to us if we were in the situation.
People’s interpretation of the meaning of a verb denoting movement of people or objects in space, such as
to approach
, depends on their situation models. For example, comprehenders interpret the meaning of
approach
differently in
The tractor is just approaching the fence
than in
The mouse is just approaching the fence
. Specifically, they interpret the distance between the figure and the landmark as being longer when the figure is large (tractor) compared with when it is small (mouse). The comprehenders’ interpretation also depends on the size of the landmark and the speed of the figure (Morrow & Clark, 1988). Apparently, comprehenders behave as if they are actually standing in the situation, looking at the tractor or mouse approaching a fence.
Time
We assume by default that events are narrated in their chronological order, with nothing left out. Presumably this assumption exists because this is how we experience events in everyday life. Events occur to us in a continuous flow, sometimes in close succession, sometimes in parallel, and often partially overlapping. Language allows us to deviate from chronological order, however. For example, we can say, “Before the psychologist submitted the manuscript, the journal changed its policy.” The psychologist submitting the manuscript is reported first, even though it was the last of the two events to occur. If people construct a situation model, this sentence should be more difficult to process than its chronological counterpart (the same sentence, but beginning with “After”). Recent neuroscientific evidence supports this prediction. Event-related brain potential (ERP) measurements indicate that “before” sentences elicit, within 300 ms, greater negativity than “after” sentences. This difference in potential is primarily located in the left anterior part of the brain and is indicative of greater cognitive effort (Münte, Schiltz, & Kutas, 1998). In real life, events follow each other seamlessly. However, narratives can have temporal discontinuities, when writers omit events not relevant to the plot. Such temporal gaps, typically signalled by phrases such as
a few days later
, are quite common in narratives. Nonetheless, they present a departure from everyday experience. Therefore, time shifts should lead to (minor) disruptions of the comprehension process. And they do. Reading times for sentences that introduce a time shift tend to be longer than those for sentences that do not (Zwaan, 1996).
All other things being equal, events that happened just recently are more accessible to us than events that happened a while ago.
Thus, in a situation model, enter should be less accessible after An hour ago, John entered the building than after A moment ago, John entered the building.
Recent probe-word recognition experiments support this prediction (e.g., Zwaan, 1996).
Causation
As we interact with the environment, we have a strong tendency to interpret event sequences as causal sequences. It is important to note that, just as we infer the goals of a protagonist, we have to infer causality; we cannot perceive it directly. Singer and his colleagues (e.g., Singer, Halldorson, Lear, & Andrusiak, 1992) have investigated how readers use their world knowledge to validate causal connections between narrated events. Subjects read sentence pairs, such as 1a and then 1b or 1a’ and then 1b, and were subsequently presented with a question like 1c:
(1a) Mark poured the bucket of water on the bonfire.
(1a’) Mark placed the bucket of water by the bonfire.
(1b) The bonfire went out.
(1c) Does water extinguish fire?
Subjects were faster in responding to 1c after the sequence 1a-1b than after 1a’-1b. According to Singer, the reason for the speed difference is that the knowledge that water extinguishes fire was activated to validate the events described in 1a-1b. However, because this knowledge cannot be used to validate 1a’-1b, it was not activated when subjects read that sentence pair.
Intentionality
We are often able to predict people’s future actions by inferring their intentionality, i.e. their goals. For example, when we see a man walking over to a chair, we assume that he wants to sit, especially when he has been standing for a long time. Thus, we might generate the inference “He is going to sit.” Keefe and McDaniel (1993) presented subjects with sentences like
After standing through the 3-hr debate, the tired speaker walked over to his chair (and sat down)
and then with probe words (e.g., sat, in this case). Subjects took about the same amount of time to name sat when the clause about the speaker sitting down was omitted and when it was included. Moreover, naming times were significantly faster in both of these conditions than in a control condition in which it was implied that the speaker remained standing.
Protagonists and Objects
Comprehenders are quick to make inferences about protagonists, presumably in an attempt to construct a more complete situation model. Consider, for example, what happens after subjects read the sentence
The electrician examined the light fitting
. If the following sentence is
She took out her screwdriver
, their reading speed is slowed down compared with when the second sentence is
He took out his screwdriver
. This happens because she provides a mismatch with the stereotypical gender of an electrician, which the subjects apparently inferred while reading the first sentence (Carreiras, Garnham, Oakhill, & Cain, 1996).
Comprehenders also make inferences about the emotional states of characters.
For example, if we read a story about Paul, who wants his brother Luke to be good in baseball, the concept of “pride” becomes activated in our mind when we read
that Luke receives the Most Valuable Player Award (Gernsbacher, Goldsmith, & Robertson, 1992).
Thus, just as in real life, we make inferences about people’s emotions when we comprehend stories.


4.14: IV Glossary
Airborne precautions: Transmission-based precautions used for clients with diagnosed or suspected pathogens spread by very small airborne particles from nasal and oral secretions that can float long distances through the air, such as measles and tuberculosis.
Blood-borne pathogens: Infectious microorganisms in blood and body fluids that can cause disease, including hepatitis B (HBV), hepatitis C (HCV), and human immunodeficiency virus (HIV).
Carrier: An individual who is colonized with an infectious agent.
Chain of infection: The process of how an infection spreads based on six links of transmission: Infectious Agent, Reservoir, Portal of Exit, Modes of Transmission, Portal of Entry, and Susceptible Host.
Colonization: A condition when a person carries an infectious agent but is not symptomatic or ill.
Contact precautions: Transmission-based precautions used for clients with known or suspected infections transmitted by touch such as C-difficile (C-diff), methicillin-resistant staphylococcus aureus (MRSA), vancomycin resistant enterococcus (VRE), or norovirus .
Disinfection: The removal of microorganisms. However, disinfection does not destroy all spores and viruses.
Doff: Take off personal protective equipment (PPE).
Don: Put on personal protective equipment (PPE).
Droplet precautions: Transmission-based precautions used for clients with a diagnosed or suspected pathogen that is spread in small droplets from sneezing or in oral and nasal secretions, such as influenza or pertussis.
Eye protection: Face shields, visors attached to masks, and goggles that are used to protect the eyes from blood or body fluids.
Fever: A temperature of 38 degrees Celsius (100.4 degrees F).
Hand hygiene: The process of removing, killing, or destroying microorganisms or visible contaminants from the hands. There are two hand-hygiene techniques: handwashing with soap and water and the use of alcohol-based hand rub (ABHR).
Healthcare-associated infection (HAI): An infection that develops in an individual after admission to a health care facility or undergoing a medical procedure.
Infection control: Methods to prevent or stop the spread of infections in health care settings.
Infectious agent: Microorganisms, such as bacteria, viruses, fungi, or parasites that can cause infectious disease.
Inflammation: Redness, warmth, swelling, and tenderness associated with early signs of infection.
Isolation gowns: Protective garments worn to protect clothing from the splashing or spraying of body fluids and reduce the transmission of microorganisms.
Malaise: A feeling of discomfort, illness, or lack of well-being that is often associated with infection.
Masks: Protective coverings worn by health care providers to protect the mucous membranes of their nose and mouth.
Medical asepsis: Techniques used to prevent the transfer of microorganisms from one person or object to another but do not completely eliminate microorganisms.
Mode of transmission: The way an infectious agent travels to other people and places.
Moments of hand hygiene: Appropriate times during patient care to perform hand hygiene, including immediately before touching a patient; before performing an aseptic task; before moving from a soiled body site to a clean body site; after touching a patient or their immediate environment; after contact with blood, body fluids, or contaminated surfaces (with or without glove use); and immediately after glove removal.
Nonspecific defenses: Generic barriers that prevent pathogens from entering the body, including physical, mechanical, or chemical barriers.
PAPR: An air-purifying respirator that uses a blower to force air through filter cartridges or canisters into the breathing zone of the wearer. This process creates an air flow inside either a tight-fitting facepiece or loose-fitting hood or helmet, providing a higher level of protection against aerosolized pathogens.
Perineal care: Cleansing the genital and rectal areas of the body.
Personal protective equipment (PPE): Specialized clothing or equipment used to prevent the spread of infection, including gloves, gowns, facial protection (masks and eye protection), and respirators.
Portal of entry: The route by which an infectious agent enters a new host.
Portal of exit: The route by which an infectious agent escapes or leaves the reservoir.
Purulent drainage: Yellow, green, or brown drainage associated with signs of infection.
Reservoir: The host in which infectious agents live, grow, and multiply.
Respirator masks: Masks with N95 or higher filtration worn by health care professionals to prevent inhalation of infectious small airborne particles.
Respiratory hygiene: Methods to prevent the spread of respiratory infections, including coughing/sneezing into the inside of one’s elbow or covering one’s mouth/nose with a tissue when coughing and promptly disposing of used tissues. Hand hygiene should be immediately performed after contact with one’s respiratory secretions. A coughing person should also wear a surgical mask to contain secretions.

Standard precautions: Precautions used by health care workers during client care when contact or potential contact with blood or body fluids may occur based on the principle that all blood, body fluids (except sweat), nonintact skin, and mucous membranes may contain transmissible infectious agents. These precautions reduce the risk of exposure for the health care worker and protect patients from potential transmission of infectious organisms.
Sterilization: A process used on equipment and the environment that destroys all pathogens, including spores and viruses. Sterilization methods include steam, boiling water, dry heat, radiation, and chemicals.
Surgical asepsis: The absence of all microorganisms during any type of invasive procedure; used for equipment used during invasive procedures, as well as the environment.
Susceptible host: A person at elevated risk of developing an infection when exposed to an infectious agent.
Transmission-based precautions: Specific types of personal protective equipment (PPE) and practices used with clients with specific types of infectious agents based on the pathogen’s mode of transmission.


9.3: A Single Population Mean using the Student t-Distribution
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In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation \(s\) as an estimate for \(\sigma\) and proceeded as before to calculate a confidence interval with close enough results. However, statisticians ran into problems when the sample size was small. A small sample size caused inaccuracies in the confidence interval.
William S. Goset (1876–1937) of the Guinness brewery in Dublin, Ireland ran into this problem. His experiments with hops and barley produced very few samples. Just replacing \(\sigma\) with \(s\) did not produce accurate results when he tried to calculate a confidence interval. He realized that he could not use a normal distribution for the calculation; he found that the actual distribution depends on the sample size. This problem led him to "discover" what is called the Student's t-distribution. The name comes from the fact that Gosset wrote under the pen name "Student."
Up until the mid-1970s, some statisticians used the normal distribution approximation for large sample sizes and only used the Student's \(t\)-distribution only for sample sizes of at most 30. With graphing calculators and computers, the practice now is to use the Student's t-distribution whenever \(s\) is used as an estimate for \(\sigma\). If you draw a simple random sample of size \(n\) from a population that has an approximately a normal distribution with mean \(\mu\) and unknown population standard deviation \(\sigma\) and calculate the \(t\)-score
\[t = \dfrac{\bar{x} - \mu}{\left(\dfrac{s}{\sqrt{n}}\right)},\]
then the \(t\)-scores follow a Student's t-distribution with \(n – 1\) degrees of freedom. The \(t\)-score has the same interpretation as the z -score. It measures how far \(\bar{x}\) is from its mean \(\mu\). For each sample size \(n\), there is a different Student's t-distribution.
The degrees of freedom, \(n – 1\), come from the calculation of the sample standard deviation \(s\). In 2.8 , we used \(n\) deviations (\(x - \bar{x}\) values) to calculate \(s\). Because the sum of the deviations is zero, we can find the last deviation once we know the other \(n – 1\) deviations. The other \(n – 1\) deviations can change or vary freely. We call the number \(n – 1\) the degrees of freedom (df).
For each sample size \(n\), there is a different Student's t-distribution.
Properties of the Student's \(t\)-Distribution
- The graph for the Student's \(t\)-distribution is similar to the standard normal curve.
- The mean for the Student's \(t\)-distribution is zero and the distribution is symmetric about zero.
- The Student's \(t\)-distribution has more probability in its tails than the standard normal distribution because the spread of the \(t\)-distribution is greater than the spread of the standard normal. So the graph of the Student's \(t\)-distribution will be thicker in the tails and shorter in the center than the graph of the standard normal distribution.
- The exact shape of the Student's \(t\)-distribution depends on the degrees of freedom. As the degrees of freedom increases, the graph of Student's \(t\)-distribution becomes more like the graph of the standard normal distribution.
- The underlying population of individual observations is assumed to be normally distributed with unknown population mean \(\mu\) and unknown population standard deviation \(\sigma\). The size of the underlying population is generally not relevant unless it is very small. If it is bell shaped (normal) then the assumption is met and
Visually Compare the Student's \(t\)-Distribution with the normal distribution
The graphs below show the standard normal distribution in black and the student's \(t\) distribution in red. Move the slider to see how changing the sample size, and thus the degrees of freedom, changes the student's \(t\) distribution.
n = 10, df = 9
Calculators and computers can easily calculate any Student's \(t\) -probabilities.
The notation for the Student's t-distribution (using T as the random variable) is:
- \(T \sim t_{df}\) where \(df = n – 1\).
- For example, if we have a sample of size \(n = 20\) items, then we calculate the degrees of freedom as \(df = n - 1 = 20 - 1 = 19\) and we write the distribution as \(T \sim t_{19}\).
If the population standard deviation is not known , the error bound for a population mean is:
- \(E = \left(t_{ \alpha/2 }\right)\left(\frac{s}{\sqrt{n}}\right)\),
- \(t_{ \alpha/2 }\) is the \(t\)-score with area to the right equal to \(\frac{\alpha}{2}\),
- use \(df = n – 1\) degrees of freedom, and
- \(s =\) sample standard deviation.
The format for the confidence interval is:
\[(\bar{x} - E, \bar{x} + E).\]
Example \(\PageIndex{1}\): Acupuncture
Suppose you do a study of acupuncture to determine how effective it is in relieving pain. You measure sensory rates for 15 subjects with the results given. Use the sample data to construct a 95% confidence interval for the mean sensory rate for the population (assumed normal) from which you took the data.
8.6; 9.4; 7.9; 6.8; 8.3; 7.3; 9.2; 9.6; 8.7; 11.4; 10.3; 5.4; 8.1; 5.5; 6.9
Answer
Use Confidence Interval for a Mean With Data .
Enter the data separated by commas (The semicolons need to be replaced with commas.)
Enter 0.95 for CL.
Hit Calculate
The 95% confidence interval is (7.3006, 9.1527)
With 95% confidence, the population mean sensory rate for people who receive acupuncture is between 7.3006 and 9.1527.
CONFIDENCE INTERVAL Calculator WITH STATISTICS (Sigma unknown)
Fill in the sample size (n), the sample mean (\(\bar{x}\)), the sample standard deviation (s), and the confidence level (CL). Write the confidence level as a decimal. For example, for a 95% confidence level, enter 0.95 for CL. Then hit Calculate and assuming the population is normally distributed, the confidence interval will be calculated for you.
| n: | \(\bar{x}\): | s: | CL: |
| Lower Bound | Upper Bound |
CONFIDENCE INTERVAL Calculator WITH DATA (sigma unknown)
Type in the values from the data set separated by commas, for example, 2,4,5,8,11,2. Then type in the confidence level, CL, and hit Calculate. Write the confidence level as a decimal. For example, for a 95% confidence level, enter 0.95 for CL.
Data:
| CL: | \(\bar{x}\): | s: | Lower Bound | Upper Bound |
Exercise \(\PageIndex{2}\)
You do a study of hypnotherapy to determine how effective it is in increasing the number of hours of sleep subjects get each night. You measure hours of sleep for 12 subjects with the following results. Construct a 95% confidence interval for the mean number of hours slept for the population (assumed normal) from which you took the data.
8.2; 9.1; 7.7; 8.6; 6.9; 11.2; 10.1; 9.9; 8.9; 9.2; 7.5; 10.5
Answer
(8.1634, 9.8032)
Example \(\PageIndex{2}\): The Human Toxome Project
The Human Toxome Project (HTP) is working to understand the scope of industrial pollution in the human body. Industrial chemicals may enter the body through pollution or as ingredients in consumer products. In October 2008, the scientists at HTP tested cord blood samples for 20 newborn infants in the United States. The cord blood of the "In utero/newborn" group was tested for 430 industrial compounds, pollutants, and other chemicals, including chemicals linked to brain and nervous system toxicity, immune system toxicity, and reproductive toxicity, and fertility problems. There are health concerns about the effects of some chemicals on the brain and nervous system. The table below shows how many of the targeted chemicals were found in each infant’s cord blood.
| 79 | 145 | 147 | 160 | 116 | 100 | 159 | 151 | 156 | 126 |
| 137 | 83 | 156 | 94 | 121 | 144 | 123 | 114 | 139 | 99 |
Use this sample data to construct a 90% confidence interval for the mean number of targeted industrial chemicals to be found in an in infant’s blood.
Answer
Use Confidence Interval for a Mean With Data .
Enter the data separated by commas (The semicolons need to be replaced with commas.)
Enter 0.90 for CL.
Hit Calculate
The 90% confidence interval is (7.3006, 9.1527)
We estimate with 90% confidence that the population mean number of all targeted industrial chemicals found in cord blood in the United States is between 117.412 and 137.488.
Exercise \(\PageIndex{2}\)
A random sample of statistics students were asked to estimate the total number of hours they spend watching television in an average week. The responses are recorded in Table. Use this sample data to construct a 98% confidence interval for the mean number of hours statistics students will spend watching television in one week.
| 0 | 3 | 1 | 20 | 9 |
| 5 | 10 | 1 | 10 | 4 |
| 14 | 2 | 4 | 4 | 5 |
Answer
Use Confidence Interval for a Mean With Data .
Enter the data separated by commas (The semicolons need to be replaced with commas.)
Enter 0.98 for CL.
Hit Calculate
The 98% confidence interval is (2.397, 9.869)
We estimate with 98% confidence that the population mean number of all hours that statistics students spend watching television in one week is between 2.397 and 9.869.
Reference
- “America’s Best Small Companies.” Forbes, 2013. Available online at http://www.forbes.com/best-small-companies/list/ (accessed July 2, 2013).
- Data from Microsoft Bookshelf .
- Data from http://www.businessweek.com/ .
- Data from http://www.forbes.com/ .
- “Disclosure Data Catalog: Leadership PAC and Sponsors Report, 2012.” Federal Election Commission. Available online at http://www.fec.gov/data/index.jsp (accessed July 2,2013).
- “Human Toxome Project: Mapping the Pollution in People.” Environmental Working Group. Available online at http://www.ewg.org/sites/humantoxome...tero%2Fnewborn (accessed July 2, 2013).
- “Metadata Description of Leadership PAC List.” Federal Election Commission. Available online at http://www.fec.gov/finance/disclosur...pPacList.shtml (accessed July 2, 2013).
Glossary
- Degrees of Freedom (\(df\))
- the number of objects in a sample that are free to vary
- Normal Distribution
- a continuous random variable (RV) with pdf \(f(x) = \frac{1}{\sigma\sqrt{2\pi}}e^{-(x-\mu)^2/2\sigma^{2}}\), where \(\mu\) is the mean of the distribution and \(\sigma\) is the standard deviation, notation: \(X \sim N(\mu,\sigma)\). If \(\mu = 0\) and \(\sigma = 1\), the RV is called the standard normal distribution .
- Standard Deviation
- a number that is equal to the square root of the variance and measures how far data values are from their mean; notation: \(s\) for sample standard deviation and \(\sigma\) for population standard deviation
- Student's t -Distribution
- investigated and reported by William S. Gossett in 1908 and published under the pseudonym Student; the major characteristics of the random variable (RV) are:
-
- It is continuous and assumes any real values.
- The pdf is symmetrical about its mean of zero. However, it is more spread out and flatter at the apex than the normal distribution.
- It approaches the standard normal distribution as \(n\) get larger.
- There is a "family of \(t\)-distributions: each representative of the family is completely defined by the number of degrees of freedom, which is one less than the number of data.
Contributors and Attributions
-
Barbara Illowsky and Susan Dean (De Anza College) with many other contributing authors. Content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at<EMAIL_ADDRESS>.


25.1: Sonata Form
Sonata form , also known as “first-movement form,” is “[t]he most important principle of musical form, or formal type, from the Classical period well into the 20th century,” according to the Grove Music Online. The purpose of this chapter is to serve as an introduction to formal, thematic, and harmonic aspects of sonata form. We will focus on sonata form as it existed during the height of the Classical era. Further and more detailed study of sonata form occurs in higher-level music theory courses.
25.1.1 Diagram of Sonata Form
Below is a generalized diagram of sonata form, which serves as our starting point. Real-world examples will contain differences and elaborations.
It is fairly common for a piece in sonata form to have multiple secondary themes (ST1, ST2). In some sonatas, the development section features new material. Some sonatas will not have a closing theme. As we work with real world examples, you will see the ways in which composers realize sonata form. While the diagram above designates three large sections (exposition, development, recapitulation), repeat signs in sonatas from the classical era designate the sonata as a two-reprise form—the exposition repeats, then the development and recapitulation repeat as a single unit. Douglass Green, in his book Form in Tonal Music, notes the sonata’s evolution from and synthesis of rounded binary and balanced binary:
The typical sonata form, as it appeared in the 18th century, is a combination of rounded and balanced binary. It begins the return with a restatement of the opening of part one, as in the rounded binary, and it closes with a restatement of the final sections (second and closing themes) of part one transposed to the tonic, as in the balanced binary.
25.1.2 Sonatina Form
While “sonatina” is sometimes understood to mean a short sonata or an easy sonata for beginners, in terms of form, sonatina form is sonata form without the development section. Sonatina form is sometimes encountered in the second, slow movement of a larger work like a symphony, as well as in overtures. A familiar piece in sonatina form is the “Miniature Overture” from The Nutcracker by Tchaikovsky.
| Exposition | Recapitulation | ||||
| PT | ST | CT | PT | ST | CT |
| 0:00 | 0:49 | 1:28 | 1:40 | 2:30 | 3:09 |
25.1.3 Sonata Principle
Important to sonata form is sonata principle, which Charles Rosen discusses in his book Sonata Forms.
The exposition of a sonata form presents the thematic material and articulates the movement from tonic to dominant in various ways so that it takes on the character of a polarization or opposition. The essential character of this opposition may be defined as a large-scale dissonance: the material played outside the tonic (i.e., in the second group) is dissonant with respect to the center of stability, or tonic. Sonata style did not invent this concept of dissonant section , but it was the first style to make it the generating force of an entire movement. 1
Rosen continues:
The dominant is conceived as a dissonant tonality in the exposition....The polarization, in fact, leads to the concept of a dissonant section , which raises the dissonant interval or chord to a higher power: that is, a simple reintroduction of the tonic key will no longer serve as a resolution, but the section outside the tonic needs to be resolved as a whole. 2
25.1.4 The Monothematic Sonata
Haydn was especially fond of restating the Primary Theme in the dominant where the Secondary Theme would normally occur. This reinforces the idea that the tonal design of a sonata was as important as thematic design.


1.2: Sets and Set Notation
Sets
A set is a well-defined collection of objects called the set's elements .
Here, "well-defined" means that someone has defined a rule or explicitly given written a set so that there is no misunderstanding as to what elements belong to the set.
- The Verbal Method: Use a sentence to define a set.
- The Roster Method: Begin with a left brace, \( \{ \), list each element of the set only once , and then end with a right brace, \( \} \).
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The Set-Builder Method:
A combination of the verbal and roster methods using a
dummy variable
such as \(x\). Set-builder notation is written as \( \{ x \mid \, \text{condition on } x \} \) and is read as\[ \begin{array}{ccccc}
\{ & x & \mid & \text{condition on }x & \} \\[6pt]
\uparrow & \uparrow & \uparrow & \uparrow & \uparrow \\[6pt]
\text{The set of} & x & \text{such that} & \text{condition on }x & \left( \text{this closing brace lets us know we are done defining the set} \right) \\[6pt]
\end{array} \nonumber \]
Let \(S\) be the set described verbally as the set of letters that make up the word "smolko".
- Create a description of \( S \) using roster notation.
- Create a desctiption of \( S \) using set-builder notation.
- Solution
-
- A description of \(S\) using roster notation would be \(\left\{ s, m, o, l, k \right\}\). We listed "o" only once, even though it appears twice in "smolko". Also, the order of the elements doesn't matter, so \(\left\{ k, l, m, o, s \right\}\) is also a roster description of \(S\).
- A description of \(S\) using set-builder notation is:\[\{ x \mid x \text{ is a letter in the word "smolko".} \}. \nonumber \]Thus, we would read\[\{ x \mid x \text{ is a letter in the word "smolko".} \}. \nonumber \]as "The set of elements \(x\) such that \(x\) is a letter in the word 'smolko'."
In each of the above cases, we may use the familiar equals sign, \( = \), and write \(S = \left\{ s, m, o, l, k \right\}\) or \(\ S=\{x \mid x \text { is a letter in the word "smolko". }\}\). This way, we do not have to write out the roster or set-builder notation when referring to the set. Instead, we can just call the set \(S\). Now, clearly \(m\) is in \(S\) and \(q\) is not in \(S\); however, how do we mention this symbolically? This is where some symbols from symbolic logic and set theory creep in.
The symbol \( \in \) , read as "belongs to," is used to denote that an element belongs to a set. The symbol \( \notin \) , read as "does not belong to," explicitly states that a given element does not belong to a set.
Thus, for the set from Example \( \PageIndex{ 1 } \), we write \(m \in S\) and \(q \notin S\). Another way to read these is "in" and "not in" for \(\in\) and \(notin\), respectively.
Intersections and Unions of Sets
Suppose \(A\) and \(B\) are two sets.
- The intersection of \(A\) and \(B\): \(A \cap B = \{ x \mid x \in A \text{ and } x \in B \}\)
- The union of \(A\) and \(B\): \(A \cup B = \{ x \mid x \in A \text{ or } x \in B \text{ (or both)} \}\)
Said differently, the intersection of two sets is the overlap of the two sets – the elements that the sets have in common. The union of two sets consists of the totality of the elements in each set collected together. See Figure \( \PageIndex{1} \) below.
Figure \( \PageIndex{1} \): A Venn Diagram of the sets \( A \) (the leftmost ellipse) and \( B \) (the rightmost ellipse). The intersection, \( A \cap B \), is the white region. The union, \( A \cup B \), is the combination of the yellow, white, and blue regions.
Let \(A = \{ 1,2,3 \}\) and \(B = \{2,4,6 \}\).
- Find \( A \cap B \).
- Find \( A \cup B \).
- Solution
-
- The only element that appears simultaneously in both sets is \( 2 \). Therefore, \( A \cap B = \{ 2 \} \).
- The union of these two sets is the collection of all elements from the sets,\[ \{1, 2, 3, 4, 6 \}. \nonumber \]Note that we do not write \( 2 \) twice, despite it appearing in \( A \) and \( B \). With roster notation, you do not write duplicates.


1.3: Redshifts
We introduced an expanding spacetime in the previous chapter. Now we begin to work out observational consequences of living in such a spacetime. In this and the next few chapters we will derive Hubble's Law, \(v=H_0 d\). In fact, we will derive a more general version of it valid for arbitrarily large distances.
Here we continue to work with just one spatial dimension. Assuming a homogeneous universe we have the same invariant distance rule as before:
\[ds^2 = -c^2 dt^2 + a^2(t)dx^2.\label{eqn:InvDistFRW1}\]
We derive in this chapter how the wavelength of light stretches over time, due to the expansion of the universe. This is called the cosmological redshift. We will find that the cosmological redshift is a very simple function of the scale factor at the time of emission divided by the scale factor at the time of reception. In other words, redshift tells us how much the universe expanded since light left the object we are observing.
In general, whether its origin is the expansion of space or the motion of an object, redshift is a quantification of the stretching of the wavelength of light. We use the symbol \(z\) to denote redshift and define it as:
\[z \equiv (\lambda_{\rm received} - \lambda_{\rm emitted})/\lambda_{\rm emitted}.\]
We see in the figure below (from NASA and Space Telescope Science Institute) some model spectra of galaxies with redshifts of 10, 11, and 12. One can see in the image that the same spectral features appear at longer wavelengths as the redshift increases. These features all had the same wavelength when emitted, but those wavelengths get stretched by the expansion to longer wavelengths. The further away the objects, the greater the stretching that occurs. We will explore this relationship between distance and redshift in chapter 1.7
Next we want to derive the relationship between redshift and expansion for light that leaves an object at rest at time \(t_e\) and is observed today by an observer at rest at time \(t_r\). To help us get there we will first introduce what we call "conformal time" and then discuss the value of the invariant distance on paths traveled by light.
Note
By "at rest" we mean at rest in the coordinate system that has an invariant distance of the form in Equation \ref{eqn:InvDistFRW1}. This frame is called "cosmic rest." Note that for a frame that is moving with respect to cosmic rest, slices of constant time would be different, and we'd no longer have this simple form where the scale factor only depends on the time coordinate.
Conformal Time
You will recall from the previous chapter that in an expanding spacetime, light does not travel on straight lines. For calculational purposes, as we will see, it would be nicer if it did move on straight lines. Well, with a change of coordinates, it can! For this purpose, we introduce a coordinate called "conformal time." The conformal time, \(\eta\), is defined via \(d\eta = dt/a(t)\). In a conformal time diagram, for the expanding spacetime with which we have been working, light trajectories are straight lines. We will find that this is a very useful property.
Box \(\PageIndex{1}\)
Exercise 3.1.1: Given a spacetime described by Equation \ref{eqn:InvDistFRW1}, work out the invariant distance specified for \(\eta,x\) labeling instead of \(t,x\) labeling. You should find \( ds^2 = a^2(\eta)[-c^2 d\eta^2 + dx^2] \) where by \(a(\eta)\) we just mean \(a(t(\eta))\). Note that \(a(\eta)\) is simply shorthand for \(a(t(\eta))\).
Beware : in previous versions of this textbook we used \(\tau\) for conformal time and it's possible that in some places we still have the old notation. I found that the use of \(\tau\) caused some confusion for students because they have seen that used before for proper time, and these are not the same thing.
The Invariant Distance for Light Trajectories
The invariant distance for a path taken by a photon is always zero. You know this is true in special relativity where \(ds^2 = -c^2 dt^2 + dx^2\). Light always travels at the speed of light, so we always have \(dx = \pm c dt\), which in turn ensures that \(ds^2 = -c^2 dt^2 + c^2 dt^2 = 0\). To see that this is true more generally, first note that for an observer at rest in a given coordinate system, and given our physical interpretation of the invariant distance, the equation for the invariant distance can always be written schematically in terms of the trajectory of a moving object as
\(ds^2\) = \(-c^2\)(infinitesimal time elapsed)\(^2\) + (infinitesimal spatial distance traversed)\(^2\)
where by "infinitesimal time elapsed" we mean as measured by a clock that is not moving in the given coordinate system and by "infinitesimal spatial distance traveled" we mean as measured by a ruler that is not moving in the given coordinate system. You can immediately see that this is true in two steps. First, consider a purely spatial separation (in the given coordinate system). The invariant distance rule then tells you that the invariant distance squared is the square of the distance between the two points as measured by a ruler at rest in that coordinate system. This verifies the second term on the right-hand side of the above equation. Second, consider a purely temporal separation. The invariant distance rule tells you that the square of the invariant distance divided by \(-c^2\) gives the square of the time elapsed on a clock moving between these two points. This verifies the first term on the right-hand side of the above equation.
You know that in the special theory of relativity that all observers see light moving at speed \(c\). A version of this is true in general relativity. We just have to be careful to state it more locally. In the general theory, any observer seeing light pass right by them (through their location), will see it traveling with speed \(c\). Since this is true for all observers, it is also true for an observer at rest in the given coordinate system, so they will see (infinitesimal spacial distance traversed) = \(c \times\) (infinitesimal time elapsed). Putting this together with the above schematic equation for \(ds^2\) we see that for a light trajectory, \(ds^2 = 0\).
Box \(\PageIndex{2}\)
Exercise 3.2.1: Draw how light rays move on a plot of \(x\) vs. \(\eta\) assuming our homogeneous expanding spacetime with one spatial dimension. Start from \(ds^2=0\) to find the relationship between \(d\eta\) and \(dx\), then draw a trajectory consistent with that relationship.
The theoretical relationship between redshift and scale factor history
We are all set up now to show, through the next three exercises, how redshift is related to the expansion that occurs between the time of emission of the light \(t_{\rm e}\), and the time of reception of the light, \(t_{\rm r}\). We will find the following very simple relationship stating that the wavelength has been increased by exactly the same factor by which the scale factor has increased; i.e.,
\[1+z \equiv \lambda_{\rm r}/\lambda_{\rm e} = a(t_{\rm r})/a(t_{\rm e}).\]
Box \(\PageIndex{3}\)
Exercise 3.3.1: Show that if \(\Delta t_e\) is the time interval between emitted light pulses (as measured by a stationary observer located where the emission is happening) and if \(\Delta t_r\) is the time interval between reception of first pulse and second pulse (as measured by a stationary observer located where the reception is occurring) then \(\Delta t_r/\Delta t_e = a(t_r)/a(t_e)\). To do so, use conformal time defined by \(d\eta = dt/a(t)\) and draw the pulse trajectories on an \(x\) vs. \(\eta\) diagram. By stationary observer we mean one that is at a constant value of \(x\); i.e., is at rest in the cosmic rest frame. You can assume that \(\Delta t_r\) and \(\Delta t_e\) are very short time scales compared to the time scale over which \(a(t)\) changes appreciably. Practical applications of this result often have \(a(t)\) changing on billion-year time scales and the \(\Delta t\)s shorter than nanoseconds so this assumption is well justified!
Box \(\PageIndex{4}\)
Exercise 3.4.1: Imagine propagation of electromagnetic waves. Use the above result to show that the wavelength of the waves emitted at time \(t_r\) and observed at time \(t_e\) is stretched so that:
\[\begin{equation*}
\begin{aligned}
z \equiv (\lambda_{\rm received} - \lambda_{\rm emitted})/\lambda_{\rm emitted} = a(t_r)/a(t_e) - 1
\end{aligned}
\end{equation*}\]
Hint: think about what happens to the period of the wave first, and then go from that to wavelength using the fact that wavelength is proportional to period.
Box \(\PageIndex{5}\)
Exercise 3.5.1: The most distant object for which a redshift has been measured is called a gamma-ray burst and it has a redshift of \(z=8.2\). By what factor has the universe expanded since light left that object?
We have just worked out the amazing fact that if we can identify a spectral line and measure its wavelength, then we can directly determine how much the universe has expanded since light left the object. Rearranging the result from Exercise 2.2.1 a little we can express this amazing fact as an equation:
\[1+ z = \lambda_{r}/\lambda_{e} = a(t_r)/a(t_e). \]
Look again at the figure above and notice that the more distant the object, the higher the redshift. This is because the more distant the object, the more time it took light to get to us from the object, and therefore the smaller the scale factor was at the time the light left the object, \(t_e\).
Before closing this section, we remind the reader of how redshifts due to the Dopper effect are related to speed -- a result we will use later in deriving Hubble's Law. If a source is moving away from you at speed v and emitting pulses with period \(T\), then the second pulse has to travel a distance \(vT\) further to get to you than was the case for the first pulse. So it's arrival will be delayed by a time \(vT/c\). Thus the period for the arriving pulses is \(T(1+v/c)\). Since wavelength is proportional to period this means the wavelength is stretched by a factor of \(1+v/c\), which means, by definition of the redshift \(z\), that \(z = v/c\). Note that our derivation has ignored the effect of relativistic time dilation. If the source had period \(T\) at rest, then if it were moving with speed \(v\) with respect to us, in our frame the period would be stretched to \(\gamma T\) and so the complete expression for \(z\) from the Doppler effect is \(1+z = \gamma (1+v/c)\). But we are only interested in this expression for small \(v/c\), for which \(\gamma \sim 1.\)
Summary
- In an expanding homogeneous and isotropic universe, the ratio between the wavelength of light emitted by an observer at cosmic rest, \(\lambda_e\) at time \(t_e\) and the wavelength as measured by an observer at cosmic rest \(\lambda_r\) at time \(t_r\) is given by \[1+z \equiv \lambda_r/\lambda_e = a(t_r)/a(t_e)\] where \(a(t)\) is the scale factor at time \(t\) and the above equation defines the redshift \(z\). We can think of this as the wavelength stretching with the expansion.
- In a non-expanding universe, a source moving away from an observer with \(v/c \ll 1\) has its light redshifted (wavelength stretched) by \[\lambda_r/\lambda_e= 1+v/c\] which is the normal Doppler effect you have studied before. What this implies is that if we interpret a small redshift \(z\) caused by the expansion of space as due to an ordinary motion-induced Dopper effect we will set \(z=v/c\). We will use this relationship later in our derivation of Hubble's Law: \(v = H_0 d\). The next thing we need for Hubble's law is how to measure distances, and how those measurements depend on theoretical quantities.
Additional Resources
You can look at images and spectra of galaxies in the Sloan Digital Sky Survey here . The spectra include identification of emission and absorption lines (with the atoms or ions responsible for them) and measurements of the redshift. To find the spectra and images, look for the table and click on the Object ID.
Quasar absorption line systems have particularly interesting spectra. You can read about them here .
HOMEWORK Problems
Problem \(\PageIndex{1}\)
A phenomenon closely related to cosmological redshift is cosmological time delay. Light signals arriving from events at the same location, but separated in time so one happens at \(t_e\) and the other at \(t_e + \delta t_e\), are separated by a larger time interval, \(\delta t_r > \delta t_e\). Derive how \(\delta t_r/\delta t_e\) depends on \(a(t_r)/a(t_e)\).  You can assume \( \delta t_r \) and \(\delta t_e\) are both much smaller than time scales over which \(a(t)\) changes appreciably.
Problem \(\PageIndex{2}\)
A supernova is observed today to take 20 days to reach peak brightness from the beginning of the explosion. It has a redshift of \(z=1\). At the location of the supernova, back when the explosion occurred, how many days did it take to go from beginning of explosion to peak brightness?


6.3.11: Critical Thinking Case
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The Ohio Connection
Janey worked as an executive assistant to a product manager at her company: Ohio Connection. Overall, she loved her job; she was happy to work with a company that provided great benefits, and she and found enjoyment in her day-to-day work. She had the same product manager boss for years, but last year, her manager left Ohio Connection and retired. Recently her new manager has been treating her unfairly and showcasing bullying behavior.
Yesterday, Janey came into work, and her boss decided to use their power as her manager and her “superior” to demand that she stay late to cover for him, correct reports that he had made mistakes on, and would not pay her overtime. She was going to be late to pick up her son from soccer practice if she stayed late; she told him this, and he was not happy.
Over subsequent days, her boss consistently would make comments about her performance, even though she had always had good remarks on reviews, and created a very negative work environment. The next time she was asked to stay late, she complied for fear of losing her job or having other negative impacts on her job. Janey’s situation was not ideal, but she didn’t feel she had a choice.
Questions:
- What type of power did Janey’s boss employ to get her to do the things that he wanted her to do?
-
What negative consequences are apparent in this situation and other situations where power is not
balanced in the workplace?
-
What steps should Janey take do to counteract the power struggle that is occurring with her new
manager?
Sources: A. Morin, “How to Prevent a Workplace Bully from taking Your Power,” Inc. , June 25, 2018, https://www.inc.com/amy-morin/how-to...our-power.html ; V. Giang, “The 7 Types Of Power That Shape The Workplace,” Business Insider, July 31, 2013, https://www.businessinsider.com/the-...rkplace-2013-7 ; B. Weinstein, “10 Tips for Dealing with a Bully Boss,” CIO , accessed October 13, 2018, https://www.cio.com.au/article/198499/ 10_tips_dealing_bully_boss/.


10.4: References
Contributors and Attributions
CC licensed content, Original
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(n.d.). Retrieved from www.eseanetwork.org/about/titlei
Burris, C., & Bryant, J. (2019, April 17). Asleep at the Wheel:. Retrieved from http://networkforpubliceducation.org/asleepatthewheel/
Digest of Education Statistics, 2018. (n.d.). Retrieved from https://nces.ed.gov/programs/digest/d18/tables/dt18_236.70.asp
Every Student Succeeds Act (ESSA). (n.d.). Retrieved from https://www.ed.gov/essa?src=policy
Foundation, R. W. (2018, August 06). Equity vs. Equality. Retrieved from https://www.youtube.com/watch?v=MlXZyNtaoDM
Kober, N., & Usher, A. (2012). A public education primer: Basic (and sometimes surprising) facts about the U.S. education system . Washington, DC: Center on Education Policy.
President’s FY 2018 Budget Request for the U.S. Department of Education. (2018, May 23). Retrieved from https://www2.ed.gov/about/overview/budget/budget18/index.html
The Constitution of the State of New York. (n.d.). Retrieved from https://www.dos.ny.gov/info/constitution/article_11_education.html
Title I, Part A – Improving Basic Programs Operated by Local Education Agencies. (n.d.). Retrieved from http://www.nysed.gov/budget-coordination/title-i-part-improving-basic-programs-operated-local-education-agencies


8.7E: Gammaproteobacteria
- Classify Gammaproteobacteria
Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae ( Escherichia coli ), Vibrionaceae and Pseudomonadaceae. Like all Proteobacteria, the Gammaproteobacteria are Gram-negative.
The Gammaproteobacteria comprise several medically and scientifically important groups of bacteria, such as the Enterobacteriaceae, Vibrionaceae and Pseudomonadaceae. A number of important pathogens belongs to this class, e.g. Salmonella spp. (enteritis and typhoid fever), Yersinia pestis (plague), Vibrio cholerae (cholera), Pseudomonas aeruginosa (lung infections in hospitalized or cystic fibrosis patients), and Escherichia coli (food poisoning).
The Enterobacteriaceae is a large family of Gram-negative bacteria that includes, along with many harmless symbionts, many of the more familiar pathogens, such as Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella. Other disease-causing bacteria in this family include Proteus, Enterobacter, Serratia, and Citrobacter. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the phylum Proteobacteria. Phylogenetically, in the Enterobacteriales, several peptidoglycan-less insect endosymbionts form a sister clade to the Enterobacteriaceae, but since they are not validly described, this group is not officially a taxon; examples of these species are Sodalis, Buchnera, Wigglesworthia, Baumannia and Blochmannia. Members of the Enterobacteriaceae can be trivially referred to as enterobacteria, as several members live in the intestines of animals. In fact, the etymology of the family is enterobacterium with the suffix to designate a family (aceae) — not after the genus Enterobacter (which would be “Enterobacteraceae”)— and the type genus is Escherichia.
Members of Chromatium are photosynthetic and oxidize hydrogen sulfide instead of water, producing sulfur as excrement. Some Gammaproteobacteria are methane oxidizers, and many of them are in symbiosis with geothermic ocean vent dwelling animals.
Key Points
- Gammaproteobacteria include an exceeding number of important pathogens, e.g. Salmonella, Yersinia, Vibrio, Pseudomonas aeruginosa.
- Like all Proteobacteria, the Gammaproteobacteria are Gram-negative.
- Some Gammaproteobacteria are methane oxidizers, and many of them are in symbiosis with geothermic ocean vent dwelling animals.
Key Terms
- symbiosis : A close, prolonged association between two or more organisms of different species, regardless of benefit to the members.
- pathogens : A pathogen or infectious agent (colloquially known as a germ) is a microorganism (in the widest sense, such as a virus, bacterium, prion, or fungus) that causes disease in its host. The host may be an animal (including humans), a plant, or even another microorganism.
- Gammaproteobacteria : Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae (Escherichia coli), Vibrionaceae and Pseudomonadaceae. Like all Proteobacteria, the Gammaproteobacteria are Gram-negative.