11.5: Comparisons with Traditional Research
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Positivist case research, aimed at hypotheses testing, is often criticised by natural science researchers as lacking in controlled observations, controlled deductions, replicability, and generalisability of findings—the traditional principles of positivist research. However, these criticisms can be overcome through appropriate case research designs. For instance, the problem of controlled observations refers to the difficulty of obtaining experimental or statistical control in case research. However, case researchers can compensate for such lack of controls by employing ’natural controls’. This natural control in Markus’ (1983) study was the corporate accountant who was one of the system advocates initially, but started resisting it once he moved to the controlling division. In this instance, the change in his behaviour may be attributed to his new divisional position. However, such natural controls cannot be anticipated in advance, and case researchers may overlook them unless they are proactively looking for such controls. Incidentally, natural controls are also used in natural science disciplines such as astronomy, geology, and human biology—for example, waiting for comets to pass close enough to the earth in order to make inferences about comets and their composition.
The problem of controlled deduction refers to the lack of adequate quantitative evidence to support inferences, given the mostly qualitative nature of case research data. Despite the lack of quantitative data for hypotheses testing (e.g., -tests), controlled deductions can still be obtained in case research by generating behavioural predictions based on theoretical considerations and testing those predictions over time. Markus employed this strategy in her study by generating three alternative theoretical hypotheses for user resistance, and rejecting two of those predictions when they did not match observed behaviour. In this case, the hypotheses were tested using logical propositions rather than mathematical tests, which are just as valid as statistical inferences since mathematics is a subset of logic.
Third, the problem of replicability refers to the difficulty of observing the same phenomenon considering the uniqueness and idiosyncrasy of a given case site. However, using Markus’ three theories as an illustration, a different researcher can test the same theories at a different case site, where three different predictions may emerge based on the idiosyncratic nature of the new case site, and the three resulting predictions may be tested accordingly. In other words, it is possible to replicate the inferences of case research, even if the case research site or context may not be replicable.
Fourth, case research tends to examine unique and non-replicable phenomena that may not be generalised to other settings. Generalisability in natural sciences is established through additional studies. Likewise, additional case studies conducted in different contexts with different predictions can establish generalisability of findings if such findings are observed to be consistent across studies.
Lastly, British philosopher Karl Popper described four requirements of scientific theories: theories should be falsifiable, they should be logically consistent, they should have adequate predictive ability, and they should provide better explanation than rival theories. In case research, the first three requirements can be improved by increasing the degrees of freedom of observed findings—for example, by increasing the number of case sites, the number of alternative predictions, and the number of levels of analysis examined. This was accomplished in Markus’ study by examining the behaviour of multiple groups (divisional accountants and corporate accountants) and providing multiple (three) rival explanations. Popper’s fourth condition was accomplished in this study when one hypothesis was found to match observed evidence better than the two rival hypotheses.


32.3: Mass Violence
By the end of this section, you should be able to:
- Describe the term mass violence.
- Examine U.S. mass shooting statistics.
- Examine how mass violence can impact whole communities and the population at large.
- Identify signs of emotional distress related to incidents of mass violence.
- Discuss the principles of mass casualty management.
 Mass violence often occurs without warning and can happen anywhere, impacting whole communities and the country at large. These types of disasters, which include shootings and acts of terrorism , disturb the sense of order and safety in situations that are normally nonthreatening. The impact of mass violence is far-reaching, instilling feelings of confusion, fear, and helplessness. They violate the larger community’s sense of safety and order, affecting even those without personal connections to the event (SAMHSA, n.d.). The most common manifestations of mass violence are:
- Mass shootings
- Terrorist bombings
- Mass riots
- Hijacking of aircraft, trains, buses, or other transportation services
Mass Shootings in the United States
Statistically, mass violence is uncommon, with mass shootings comprising most incidents. There is no standard definition of mass shooting, but there is a common definition for active shooter . An active shooter is an individual who is killing or attempting to kill people with a firearm within an area (USA Facts, 2023). Criteria to report mass shootings differ by the number of victims, whether injuries are included, the location of the shooting, whether it occurred with another crime, and the relationship between the shooter and the victims (Smart & Shell, 2021). More common definitions include an incident where four or more people have been murdered by a firearm or an event where at least four victims were injured or killed by a firearm. Although less than one percent of all firearm deaths annually in the United States are attributed to mass shootings, they have incited fear and panic beyond the direct victims and their families (Soni & Tekin, 2022). In the United States, the rate of mass shootings and the number of people killed over the last four decades has increased, resulting in over 1,000 deaths and 1,500 injuries (NCMDI, 2019; Soni & Tekin, 2022). Federal funds to study gun violence were largely unavailable for about 20 years, but in 2019 the U.S. Congress approved funding for the CDC and National Institutes of Health to conduct gun violence research. This opened the door to new research on gun violence, suicide, and injury prevention (Weir, 2021). Table 32.6 provides 2016–2022 statistics, highlighting the recent increase in mass shootings. Table 32.7 compares the outcomes of the deadliest mass shooting incidents in the United States.
| Source | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 |
|---|---|---|---|---|---|---|---|
| Gun Violence Archive (2023) | 383 | 348 | 336 | 417 | 610 | 690 | 647 |
| Everytown (2023) | 372 | 341 | 329 | 410 | 605 | 686 | 636 |
| *numbers vary based upon the definition of mass shooting |
| 2017 Concert in Las Vegas, NV | 60 killed | 411 wounded |
| 2016 Nightclub in Orlando, FL | 49 killed | 53 wounded |
| 2019 Store in El Paso, TX | 23 killed | 23 wounded |
| 2017 Church in Sutherland Springs, TX | 25 killed | 20 wounded |
| 2022 Elementary School in Uvalde, TX | 21 killed | 17 wounded |
| 2018 High School in Parkland, FL | 17 killed | 17 wounded |
The Impact of Mass Violence
Mass violence and shootings have significant mental health effects on population health. These terrifying and traumatic incidents are often directed at strangers in public places. The community’s response is defensive and urgent, demanding an explanation to try to make sense of the nonsensical.  It is difficult to comprehend the logic of mass violence or to imagine that a mentally stable person would intentionally kill multiple strangers; therefore, one might conclude that all perpetrators of mass violence must be mentally ill (NCMDI, 2019). However, according to a report from the U.S. Department of Homeland Security, the motives for mass violence are complex. The most common reasons relate to grievances, ideology , bias , political beliefs, and psychotic behavior (Alathari et al., 2023). Some offenders give multiple reasons for committing acts of mass violence, and others, killed during the event, never provide a reason. Table 32.8 outlines cited motivations for mass violence events. Over half are attributed to personal, domestic, or workplace grievances, while only 14 percent are related to psychotic symptoms (Alathari et al., 2023).
| Components to Motivate* | 2016 | 2017 | 2018 | 2019 | 2020 | Total |
|---|---|---|---|---|---|---|
|
Grievances
Personal Domestic Workplace |
40%
5 6 2 |
50%
9 6 6 |
68%
11 8 3 |
35%
8 1 4 |
60%
13 8 3 |
51%
46 29 18 |
| Ideological, bias-related, or political beliefs | 30% | 24% | 10% | 21% | 10% | 18% |
| Psychotic symptoms | 13% | 26% | 10% | 15% | 8% | 14% |
| Desire to kill | 13% | 8% | 3% | 9% | 3% | 7% |
| Fame or notoriety | 7% | 8% | 3% | 6% | 5% | 6% |
| Other | 3% | 3% | 10% | 9% | 8% | 6% |
| Undetermined | 20% | 8% | 10% | 29% | 23% | 18% |
| *The percentages for each year do not total 100% as some attackers had multiple motives. |
Mental health issues related to mass violence events are correlated to direct victims, their families, and the general population. Research has shown that 48 percent of Americans live with the fear of becoming a victim of a mass shooting, and more than 10 percent have avoided large crowds or bought a weapon because they are worried about the threat of mass shootings (Brenan, 2019). Individuals living in the community or attending the school where a shooting has occurred have increased emotional distress, with a higher likelihood of taking antidepressants, engaging in risky behaviors, or considering suicide (Brodeur & Yousaf, 2022; Deb & Gangaram, 2023).
Public health and community health nurses and other health providers must be aware of the role of mental illness in mass violence for both victims and offenders to provide support and lead efforts to prevent mass violence (Alathari et al., 2023). Like many other community health concerns, preparation and prevention are key strategies for combating mass violence. Planning and participation in regular preparation activities like active-shooter drills supports proactivity and preparation for the worst-case scenario (Peterson & Densley, 2021).
A part of preparation, albeit not coordinated, is attention to warning signs . Warning signs include having behavioral problems or difficulty connecting with others, being noncommunicative, having aggressive or violent verbalizations, being withdrawn, harming self or others, and being emotionally unstable (Peterson & Densley, 2021). Education and advocacy programs for teachers, caregivers, and the public can go a long way in promoting awareness of behaviors that might be precursors to violence in individuals. Seemingly innocuous comments or interactions may be warning signs or cries for help (Peterson & Densley, 2021).
Mass Casualty Management
Mass casualty incidents (MCIs) are human-made or natural disasters that overwhelm the resources of local management agencies and the health care system. Emergency medical services (EMS) are often the first responders on the scene of a mass casualty event, but the principles of response apply to any health care responder. First responders are critical in triaging, stabilizing, and preparing to transport victims to health care facilities after MCIs. As the name implies, MCIs involve large numbers of victims who will need varying levels of care. Effective management, communication, and collaboration are essential during an MCI. Local community agencies, such as the fire department or police department, may respond, and state or national agencies may also become involved, depending on the type and severity of an MCI (Alpert & Kohn, 2023).
Response to a mass casualty event is complex, involving many people from different disciplines. Planning is a critical step to response, as a methodical approach to a crisis engages community responders in thinking through the lifecycle of a potential crisis, determining required capabilities, and establishing a framework for roles and responsibilities (FEMA, 2021). Since mass casualty disasters can happen without warning, a constant state of readiness requires training and regular drills. Simulations are frequently used to prepare health care workers and first responders for mass casualty management, as individuals must understand the roles that each one has in mass casualty response (Figure 32.3).
Multiagency, Interprofessional Team Coordination
The National Incident Management System (NIMS) provides a framework for the management of disasters and MCIs. NIMS guides the multiagency, interprofessional structure and organization for communication and incident command, allowing for efficient communication using common terminology, clarification of leadership and roles, and effective management and distribution of resources. Figure 32.4 illustrates the organization of Incident Command System (ICS) used in NIMS. Table 32.9 provides further description of the roles of command staff in the ICS.
| Role | Function |
|---|---|
| Incident Command |
|
| Public Information Officer |
|
| Safety Officer |
|
| Liaison Officer |
|
| Operations Section Chief |
|
| Planning Section Chief |
|
| Logistics Section Chief |
|
| Finance/Administration Section Chief |
|
| Intelligence/Investigations Section Chief |
|
The Medical Branch (nurses and other health care staff) reports to the Operations Section Chief. This includes the medical director, who supervises triage , treatment, and transport of clients; the triage officer, who oversees triage of clients; the treatment officer, who manages the treatment area; and the transport officer, who arranges and documents transport of clients from the scene (Lincoln et al., 2023). Additional roles may be added depending upon the number of clients and the time needed to manage medical needs.
Scene Safety Considerations
When responding to a mass casualty incident, there are several issues that must be considered to effectively manage the scene and victims for optimal outcomes.
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Scene Safety
- The top priority on the scene of an MCI is the safety of the responders. Verifying that the scene is safe before first responders provide care prevents secondary incidents and subsequent injuries (Alpert & Kohn, 2023). Scene security and the responsible agency will depend on the nature of the MCI. If the event is a vehicular accident, the environment around the scene should be assessed for fuel leakage, fire hazard, and other risks that would further endanger victims or responders.
- Appropriate personal protective equipment (PPE) needs to be available and used by responders to a chemical, biological, radiological, or nuclear event.
- In response to a terrorist or mass violence attack, the possibility of an explosive detonation or a suicide bomber should be considered and bomb disposal experts dispatched before responders begin lifesaving measures.
- In a mass shooting incident, if the offender has not been apprehended or has fled the scene, first responders must not approach the scene unless they are trained in tactical medicine and are wearing appropriate protective gear.
- The response to or after a fire poses a risk of building collapse and inhalation (Alpert & Kohn, 2023).
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Field Triage
- After scene safety, mass casualty response requires field triage of victims. Examples of field triage systems will follow later in this chapter.
Nurses and other field-level providers increasingly will be called on to respond to both natural and human-made situations that involve multiple casualties. Situational awareness (SA) is necessary for managing these complicated incidents. SA is the ability to perceive, understand, and respond to the current situation. Basically, it is knowing what is going on in the environment, recognizing unsafe situations, and responding to the situation in a safe, efficient way. Situational Awareness For Emergency Response (SAFER) utilizes technology to access building information and video surveillance when responding to emergencies.
Watch the video, and then respond to the following questions.
- Why is situational awareness important when responding to a hazardous event?
- What information does SAFER give to responders?
- How can SAFER be used during response to a disaster?
Zoning of Care Areas
In an MCI, the area of care is divided into zones if there is a risk of chemical, biological, radiological, or nuclear contamination (Figure 32.5) (Alpert & Kohn, 2023).
- The hot zone is the immediate location of the incident, where victims and responders have direct contamination.
- The warm zone is the area surrounding the hot zone where contamination is present from victims or responders leaving the hot zone. Triage and decontamination can occur in the warm zone to neutralize the risk to victims.
- The cold zone is where care for victims occurs and may serve as the location for minor casualty holding or release.


8.12: Introduction to Hypothesis Test for a Population Proportion
What you’ll learn to do: Conduct a hypothesis test for a population proportion.
When we have real world data on population proportions we will have to learn when a situation calls for testing a hypothesis about a population proportion, conduct a hypothesis test and state a conclusion in context. We will interpret the P-value as a conditional probability in the context of a hypothesis test. We will then distinguish the difference between statistical significance from practical importance.
Contributors and Attributions
CC licensed content, Shared previously
- Concepts in Statistics. Provided by : Open Learning Initiative. Located at : http://oli.cmu.edu . License : CC BY: Attribution


6.5: Forming Attachments
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Attachment is the close bond with a caregiver from which the infant derives a sense of security. The formation of attachments in infancy has been the subject of considerable research as attachments have been viewed as foundations for future relationships. Additionally, attachments form the basis for confidence and curiosity as toddlers, and as important influences on self- concept.
Freud’s Psychoanalytic Theory
According to Freud (1938) infants are oral creatures who obtain pleasure from sucking and mouthing objects. Freud believed the infant will become attached to a person or object that provides this pleasure. Consequently, infants were believed to become attached to their mother because she was the one who satisfied their oral needs and provided pleasure. Freud further believed that the infants will become attached to their mothers “if the mother is relaxed and generous in her feeding practices, thereby allowing the child a lot of oral pleasure,” (Shaffer, 1985, p. 435).
Harlow’s Research
In one classic study, Wisconsin University psychologists Harry and Margaret Harlow investigated the responses of young rhesus monkeys to explore if breastfeeding was the most important factor to attachment.
The infant monkeys were separated from their biological mothers, and two surrogate mothers were introduced to their cages. The first mother (the wire mother) consisted of a round wooden head, a mesh of cold metal wires, and a bottle of milk from which the baby monkey could drink. The second mother was a foam-rubber form wrapped in a heated terry-cloth blanket. The infant monkeys went to the wire mother for food, but they overwhelmingly preferred and spent significantly more time with the warm terry-cloth mother. The warm terry-cloth mother provided no food but did provide comfort (Harlow, 1958). The infant's need for physical closeness and touching is referred to as contact comfort . Contact comfort is believed to be the foundation for attachment. The Harlows’ studies confirmed that babies have social as well as physical needs. Both monkeys and human babies need a secure base that allows them to feel safe. From this base, they can gain the confidence they need to venture out and explore their worlds.
Bowlby’s Theory
Building on the work of Harlow and others, John Bowlby developed the concept of attachment theory. He defined attachment as the affectional bond or tie that an infant forms with the mother (Bowlby, 1969). An infant must form this bond with a primary caregiver in order to have normal social and emotional development. In addition, Bowlby proposed that this attachment bond is very powerful and continues throughout life. He used the concept of a secure base to define a healthy attachment between parent and child (Bowlby, 1982).
Bowlby said that two things are needed for a healthy attachment: The caregiver must be responsive to the child’s physical, social, and emotional needs; and the caregiver and child must engage in mutually enjoyable interactions (Bowlby, 1969). Additionally, Bowlby observed that infants would go to extraordinary lengths to prevent separation from their parents, such as crying, refusing to be comforted, and waiting for the caregiver to return.
Bowlby also observed that these same expressions were common to many other mammals, and consequently argued that these negative responses to separation serve an evolutionary function. Because mammalian infants cannot feed or protect themselves, they are dependent upon the care and protection of adults for survival. Thus, those infants who were able to maintain proximity to an attachment figure were more likely to survive and reproduce.
Erikson: Trust vs. Mistrust
As previously discussed in chapter 1, Erikson formulated an eight-stage theory of psychosocial development. Erikson was in agreement on the importance of a secure base, arguing that the most important goal of infancy was the development of a basic sense of trust in one’s caregivers. Consequently, the first stage, trust vs. mistrust, highlights the importance of attachment. Erikson maintained that the first year to year and a half of life involves the establishment of a sense of trust (Erikson, 1982). Infants are dependent and must rely on others to meet their basic physical needs as well as their needs for stimulation and comfort. A caregiver who consistently meets these needs instills a sense of trust or the belief that the world is a trustworthy place. The caregiver should not worry about overly indulging a child’s need for comfort, contact or stimulation.
Problems Establishing Trust
Erikson (1982) believed that mistrust could contaminate all aspects of one’s life and deprive the individual of love and fellowship with others. Consider the implications for establishing trust if a caregiver is unavailable or is upset and ill-prepared to care for a child. Or if a child is born prematurely, is unwanted, or has physical problems that make him or her more challenging to parent. Under these circumstances, we cannot assume that the parent is going to provide the child with a feeling of trust.
Mary Ainsworth and the Strange Situation
Developmental psychologist Mary Ainsworth, a student of John Bowlby, continued studying the development of attachment in infants. Ainsworth and her colleagues created a laboratory test that measured an infant’s attachment to his or her parent. The test is called The Strange Situation because it is conducted in a context that is unfamiliar to the child and therefore likely to heighten the child’s need for his or her parent (Ainsworth, 1979).
During the procedure, which lasts about 20 minutes, the parent and the infant are first left alone, while the infant explores the room full of toys. Then a strange adult enters the room and talks for a minute to the parent, after which the parent leaves the room. The stranger stays with the infant for a few minutes, and then the parent again enters and the stranger leaves the room. During the entire session, a video camera records the child’s behaviors, which are later coded by the research team. The investigators were especially interested in how the child responded to the caregiver leaving and returning to the room, referred to as the “reunion.” On the basis of their behaviors, the children are categorized into one of four groups where each group reflects a different kind of attachment relationship with the caregiver. One style is secure and the other three styles are referred to as insecure.
- A child with a secure attachment style usually explores freely while the caregiver is present and may engage with the stranger. The child will typically play with the toys and bring one to the caregiver to show and describe from time to time. The child may be upset when the caregiver departs, but is also happy to see the caregiver return.
- A child with an ambivalent (sometimes called resistant) attachment style is wary about the situation in general, particularly the stranger, and stays close or even clings to the caregiver rather than exploring the toys. When the caregiver leaves, the child is extremely distressed and is ambivalent when the caregiver returns. The child may rush to the caregiver, but then fails to be comforted when picked up. The child may still be angry and even resist attempts to be soothed.
 The child may run away from the mother when she approaches. The child will not explore very much, regardless of who is there, and the stranger will not be treated much differently from the mother.
- A child with a disorganized/disoriented attachment style seems to have an inconsistent way of coping with the stress of the strange situation. The child may cry during the separation, but avoid the mother when she returns, or the child may approach the mother but then freeze or fall to the floor.
How common are the attachment styles among children in the United States? It is estimated that about 65 percent of children in the United States are securely attached. Twenty percent exhibit avoidant styles and 10 to 15 percent are ambivalent. Another 5 to 10 percent may be characterized as disorganized.
Some cultural differences in attachment styles have been found (Rothbaum, Weisz, Pott, Miyake, & Morelli, 2010). For example, German parents value independence and Japanese mothers are typically by their children’s sides. As a result, the rate of insecure-avoidant attachments is higher in Germany and insecure-resistant attachments are higher in Japan. These differences reflect cultural variation rather than true insecurity, however (van Ijzendoorn and Sagi, 1999).
Keep in mind that methods for measuring attachment styles have been based on a model that reflects middle-class, U. S. values and interpretation. Newer methods for assessment attachment styles involve using a Q-sort technique in which a large number of behaviors are recorded on cards and the observer sorts the cards in a way that reflects the type of behavior that occurs within the situation (Waters, 1987). There are 90 items in the third version of the Q-sort technique, and examples of the behaviors assessed include:
- When child returns to mother after playing, the child is sometimes fussy for no clear reason.
- When the child is upset or injured, the child will accept comforting from adults other than mother.
- Child often hugs or cuddles against mother, without her asking or inviting the child to do so.

At least two researchers observe the child and parent in the home for 1.5-2 hours per visit. Usually two visits are sufficient to gather adequate information. The parent is asked if the behaviors observed are typical for the child. This information is used to test the validity of the Strange Situation classifications across age, cultures, and with clinical populations.
Caregiver Consistency
Having a consistent caregiver may be jeopardized if the infant is cared for in a child care setting with a high turnover of staff or if institutionalized and given little more than basic physical care.
Infants who, perhaps because of being in orphanages with inadequate care, have not had the opportunity to attach in infancy may still form initial secure attachments several years later. However, they may have more emotional problems of depression, anger, or be overly friendly as they interact with others (O’Connor et. al., 2003).
Social Deprivation
Severe deprivation of parental attachment can lead to serious problems. According to studies of children who have not been given warm, nurturing care, they may show developmental delays, failure to thrive, and attachment disorders (Bowlby, 1982). Non-organic failure to thrive is the diagnosis for an infant who does not grow, develop, or gain weight on schedule. In addition, postpartum depression can cause even a well-intentioned mother to neglect her infant.
Reactive Attachment Disorder
Children who experience social neglect or deprivation, repeatedly change primary caregivers that limit opportunities to form stable attachments, or are reared in unusual settings (such as institutions) that limit opportunities to form stable attachments can certainly have difficulty forming attachments. According to the Diagnostic and Manual of Mental Disorders, 5th edition (American Psychiatric Association, 2013), those children experiencing neglectful situations and also displaying markedly disturbed and developmentally inappropriate attachment behavior, such as being inhibited and withdrawn, minimal social and emotional responsiveness to others, and limited positive affect, may be diagnosed with Reactive Attachment Disorder . This disorder often occurs with developmental delays, especially in cognitive and language areas. Fortunately, the majority of severely neglected children do not develop Reactive Attachment Disorder, which occurs in less than 10% of such children. The quality of the caregiving environment after serious neglect affects the development of this disorder.
Resiliency
Being able to overcome challenges and successfully adapt is resiliency . Even young children can exhibit strong resilience to harsh circumstances. Resiliency can be attributed to certain personality factors, such as an easy-going temperament. Some children are warm, friendly, and responsive, whereas others tend to be more irritable, less manageable, and difficult to console, and these differences play a role in attachment (Gillath, Shaver, Baek, & Chun, 2008; Seifer, Schiller, Sameroff, Resnick, & Riordan, 1996). It seems safe to say that attachment, like most other developmental processes, is affected by an inter play of genetic and socialization influences.
Receiving support from others also leads to resiliency. A positive and strong support group can help a parent and child build a strong foundation by offering assistance and positive attitudes toward the newborn and parent. In a direct test of this idea, Dutch researcher van den Boom (1994) randomly assigned some babies’ mothers to a training session in which they learned to better respond to their children’s needs. The research found that these mothers’ babies were more likely to show a secure attachment style in comparison to the mothers in a control group that did not receive training. 22
Contributors and Attributions
22. Lifespan Development: A Psychological Perspective by Martha Lally and Suzanne Valentine-French is licensed under CC BY-NC-SA 3.0


36.2: Points on the Number Line
Lesson
Let's plot positive and negative numbers on the number line.
Exercise \(\PageIndex{1}\): A Point on the Number Line
Which of the following numbers could be \(B\)?
\(2.5\qquad\frac{2}{5}\qquad\frac{5}{2}\qquad\frac{25}{10}\qquad 2.49\)
Exercise \(\PageIndex{2}\): What's the Temperature?
- Here are five thermometers. The first four thermometers show temperatures in Celsius. Write the temperatures in the blanks.
The last thermometer is missing some numbers. Write them in the boxes.
- Elena says that the thermometer shown here reads \(-2.5^{\circ}\text{C}\) because the line of the liquid is above \(-2^{\circ}\text{C}\). Jada says that it is \(-1.5^{\circ}\text{C}\). Do you agree with either one of them? Explain your reasoning.
- One morning, the temperature in Phoenix, Arizona, was \(8^{\circ}\text{C}\) and the temperature in Portland, Maine, was \(12^{\circ}\text{C}\) cooler. What was the temperature in Portland?
Exercise \(\PageIndex{3}\): Folded Number Lines
Your teacher will give you a sheet of tracing paper on which to draw a number line.
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Follow the steps to make your own number line.
- Use a straightedge or a ruler to draw a horizontal line. Mark the middle point of the line and label it 0.
- To the right of 0, draw tick marks that are 1 centimeter apart. Label the tick marks 1, 2, 3. . . 10. This represents the positive side of your number line.
- Fold your paper so that a vertical crease goes through 0 and the two sides of the number line match up perfectly.
- Use the fold to help you trace the tick marks that you already drew onto the opposite side of the number line. Unfold and label the tick marks -1, -2, -3. . . -10. This represents the negative side of your number line.
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Use your number line to answer these questions:
- Which number is the same distance away from zero as is the number 4?
- Which number is the same distance away from zero as is the number -7?
- Two numbers that are the same distance from zero on the number line are called opposites . Find another pair of opposites on the number line.
- Determine how far away the number 5 is from 0. Then, choose a positive number and a negative number that is each farther away from zero than is the number 5.
-
Determine how far away the number -2 is from 0. Then, choose a positive number and a negative number that is each farther away from zero than is the number -2.
Pause here so your teacher can review your work.
- Here is a number line with some points labeled with letters. Determine the location of points \(P, X,\) and \(Y\).
If you get stuck, trace the number line and points onto a sheet of tracing paper, fold it so that a vertical crease goes through 0, and use the folded number line to help you find the unknown values.
Are you ready for more?
At noon, the temperatures in Portland, Maine, and Phoenix, Arizona, had opposite values. The temperature in Portland was \(18^{\circ}\text{C}\) lower than in Phoenix. What was the temperature in each city? Explain your reasoning.
Summary
Here is a number line labeled with positive and negative numbers. The number 4 is positive, so its location is 4 units to the right of 0 on the number line. The number -1.1 is negative, so its location is 1.1 units to the left of 0 on the number line.
We say that the opposite of 8.3 is -8.3, and that the opposite of \(\frac{-3}{2}\) is \(\frac{3}{2}\). Any pair of numbers that are equally far from 0 are called opposites .
Points \(A\) and \(B\) are opposites because they are both 2.5 units away from 0, even though \(A\) is to the left of 0 and \(B\) is to the right of 0.
A positive number has a negative number for its opposite. A negative number has a positive number for its opposite. The opposite of 0 is itself.
You have worked with positive numbers for many years. All of the positive numbers you have seen—whole and non-whole numbers—can be thought of as fractions and can be located on a the number line.
To locate a non-whole number on a number line, we can divide the distance between two whole numbers into fractional parts and then count the number of parts. For example, 2.7 can be written as \(2\frac{7}{10}\). The segment between 2 and 3 can be partitioned into 10 equal parts or 10 tenths. From 2, we can count 7 of the tenths to locate 2.7 on the number line.
All of the fractions and their opposites are what we call rational numbers . For example, \(4, -1.1, 8.3, -8.3, \frac{-3}{2},\) and \(\frac{3}{2}\) are all rational numbers.
Glossary Entries
Definition: Negative Number
A negative number is a number that is less than zero. On a horizontal number line, negative numbers are usually shown to the left of 0.
Definition: Opposite
Two numbers are opposites if they are the same distance from 0 and on different sides of the number line.
For example, 4 is the opposite of -4, and -4 is the opposite of 4. They are both the same distance from 0. One is negative, and the other is positive.
Definition: Positive Number
A positive number is a number that is greater than zero. On a horizontal number line, positive numbers are usually shown to the right of 0.
Definition: Rational Number
A rational number is a fraction or the opposite of a fraction.
For example, 8 and -8 are rational numbers because they can be written as \(\frac{8}{1}\) and \(-\frac{8}{1}\).
Also, 0.75 and -0.75 are rational numbers because they can be written as \(\frac{75}{100}\) and \(-\frac{75}{100}\).
Practice
Exercise \(\PageIndex{4}\)
For each number, name its opposite.
- \(-5\)
- \(28\)
- \(-10.4\)
- \(0.875\)
- \(0\)
- \(-8,003\)
Exercise \(\PageIndex{5}\)
Plot the numbers \(-1.5, \frac{3}{2}, -\frac{3}{2},\) and \(-\frac{4}{3}\) on the number line. Label each point with its numeric value.
Exercise \(\PageIndex{6}\)
Plot these points on a number line.
- -1.5
- the opposite of -2
- the opposite of 0.5
- -2
Exercise \(\PageIndex{7}\)
-
Represent each of these temperatures in degrees Fahrenheit with a positive or negative number.
- \(5\) degrees above zero
- \(3\) degrees below zero
- \(6\) degrees above zero
- \(2\frac{3}{4}\) degrees below zero
- Order the temperatures above from the coldest to the warmest.
(From Unit 7.1.1)
Exercise \(\PageIndex{8}\)
Solve each equation.
- \(8x=\frac{2}{3}\)
- \(1\frac{1}{2}=2x\)
- \(5x=\frac{2}{7}\)
- \(\frac{1}{4}x=5\)
- \(\frac{1}{5}=\frac{2}{3}x\)
(From Unit 6.1.5)
Exercise \(\PageIndex{9}\)
Write the solution to each equation as a fraction and as a decimal.
- \(2x=3\)
- \(5y=3\)
- \(0.3z=0.009\)
(From Unit 6.1.5)
Exercise \(\PageIndex{10}\)
There are 15.24 centimeters in 6 inches.
- How many centimeters are in 1 foot?
- How many centimeters are in 1 yard?
(From Unit 3.2.3)


3: Writing Essentials Last updated Save as PDF Page ID 58173 Lumen Learning Lumen Learning 3.1: Why It Matters- Writing Essentials 3.2: Introduction to Thesis Statements and Topic Sentences 3.3: Thesis Statements 3.4: Topic Sentences 3.5: Introduction to Effective Paragraphs 3.6: Paragraph Development- Supporting Claims 3.7: Paragraphs and Paragraph Transitions 3.8: Introductions 3.9: Conclusions 3.10: Introduction to Audience Awareness 3.11: Audience Analysis 3.12: Tone, Language, and Appeal 3.13: Introduction to Writing Strong Sentences 3.14: Sentence Construction 3.15: Using the Active Voice 3.16: Putting It Together- Writing Essentials 3.17: Discussion- Thesis Statements and Supporting Claims Assignment 3.18: Discussion- Take a Stance


8.1: Pop/Rock Music Last updated Save as PDF Page ID 61985 Robin Wharton and Kris Shaffer eds. Open Music Theory via Hybrid Pedagogy Publishing 8.1.1: Rhythm - Syncopation in Pop <IP_ADDRESS>: Rhythm - Syncopation in Pop/Rock Music 8.1.2: Harmony - Harmony in Pop <IP_ADDRESS>: Harmony - Harmony in Pop/Rock Music 8.1.3: Harmony - The "50s doo-wop" Progression 8.1.4: Harmony - The Singer <IP_ADDRESS>: Harmony - The Singer/Songwriter Chord Progression 8.1.5: Harmony - The "Puff" Progression 8.1.6: Harmony - The Blues Progression 8.1.7: Harmony - The Lament Progression 8.1.8: Harmony - Circle-of-fifths Progression, Minor Mode 8.1.9: Harmony - Plagal Progressions 8.1.10: Form - Overview 8.1.11: Form - Terminology and Basic Concepts 8.1.12: Form - Formal Containers and Module Structures 8.1.13: Form - Formal Functions 8.1.14: Form - Analytical Notation


6.4: Normal Distribution - Lap Times (Worksheet)
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- Last updated
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Name: ______________________________
Section: _____________________________
Student ID#:__________________________
Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.
Student Learning Outcome
- The student will compare and contrast empirical data and a theoretical distribution to determine if Terry Vogel's lap times fit a continuous distribution.
Directions
Round the relative frequencies and probabilities to four decimal places. Carry all other decimal answers to two places.
Collect the Data
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Use the data from
Appendix C
. Use a stratified sampling method by lap (races 1 to 20) and a random number generator to pick six lap times from each stratum. Record the lap times below for laps two to seven.
_______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ _______ - Construct a histogram. Make five to six intervals. Sketch the graph using a ruler and pencil. Scale the axes.
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Calculate the following:
- \(\bar{x}\) = _______
- \(s\) = _______
- Draw a smooth curve through the tops of the bars of the histogram. Write one to two complete sentences to describe the general shape of the curve. (Keep it simple. Does the graph go straight across, does it have a v-shape, does it have a hump in the middle or at either end, and so on?)
Analyze the Distribution
Using your sample mean, sample standard deviation, and histogram to help, what is the approximate theoretical distribution of the data?
- \(X \sim\) _____(_____,_____)
- How does the histogram help you arrive at the approximate distribution?
Describe the Data
Use the data you collected to complete the following statements.
- The IQR goes from __________ to __________.
- IQR = __________. ( IQR = Q 3 – Q 1 )
- The 15 th percentile is _______.
- The 85 th percentile is _______.
- The median is _______.
- The empirical probability that a randomly chosen lap time is more than 130 seconds is _______.
- Explain the meaning of the 85 th percentile of this data.
Theoretical Distribution
Using the theoretical distribution, complete the following statements. You should use a normal approximation based on your sample data.
- The IQR goes from __________ to __________.
- IQR = _______.
- The 15 th percentile is _______.
- The 85 th percentile is _______.
- The median is _______.
- The probability that a randomly chosen lap time is more than 130 seconds is _______.
- Explain the meaning of the 85 th percentile of this distribution.
Discussion Questions
Do the data from the section titled Collect the Data give a close approximation to the theoretical distribution in the section titled Analyze the Distribution ? In complete sentences and comparing the result in the sections titled Describe the Data and Theoretical Distribution , explain why or why not.


4.1: Repackaging Newton's Second Law
Definition of Impulse
In chapter 2, we made a point of emphasizing that force is not possessed by objects – it is an interaction between them. One way we know this is that if the same force is exerted on identical objects that start at rest, the two objects are not necessarily moving the same afterward. There is an important ingredient missing here – the duration that the force acts. Since the force causes an acceleration, the longer it acts, the more the velocity is affected. So multiplying the force by the amount of time it acts may provide us with a useful quantity. The force may be changing magnitude or direction while it acts, but over a very short time this product is:
\[d\overrightarrow J = \overrightarrow F dt \]
If we want to know the totality of this quantity over a finite time interval, we need to add up all these little contributions. We give this quantity the name impulse .
Definition: Impulse
\[\overrightarrow J_{tot}\left(t_A \rightarrow t_B\right) \equiv \int \limits_{t_A}^{t_B} \overrightarrow F_{net} dt \nonumber \]
This quantity is the sum of the product of the forces and the times over which those forces act. This certainly sounds very similar to work, which takes a product of forces and displacements. Also, impulse will have an impact on the motion of the object, as work did. But there are also many differences between these two quantities.
The first difference between impulse and work is that they obviously represent different physical quantities, because they have different units. While work has units of energy which we measure in Joules (or Newton-meters), impulse has units of force-times-time, measured in Newton-seconds. A second difference is that the impulse integral (mercifully) is not a line integral – there is no "path" to concern ourselves with when computing impulse. And third, because there is no dot product involved with the impulse integral, the result is a vector, in contrast to work, which is a scalar.
Definition of Momentum
The definition of impulse is not the end of the story, any more than the definition of work was. It needs to be related to the effect it has on the motion of the object. In the case of work, this relationship was expressed as the work-energy theorem:
\[\begin{array}{l} \text{actions of pushes and pulls} && = && W_{tot}\left(A\rightarrow B\right) \\ && = && \int \limits_A^B \overrightarrow F_{net} \cdot \overrightarrow {dl} \\ && = && \frac{1}{2} mv_B^2 - \frac{1}{2} mv_A^2 \\ && = && \Delta KE \\ && = && \text{effect of pushes and pulls} \end{array} \]
For the case of impulse, we find this relationship again by coming back to Newton's second law, and noting that the integral of acceleration is velocity:
We call the quantity \(\overrightarrow p_{cm}\) the momentum of the collection of particles on which the net force is acting, defined in terms of the total mass of the collection of particles and the velocity (magnitude and direction) of the collection's center of mass. As we saw in chapter 2, Newton's 2nd law works for any collection of particles, whether they form a solid object or are completely non-interacting, like a gas. So since this result is derived from the 2nd law, the same is true here. While this definition applies to a collection of particles, it is useful to define this same quantity for individual particles as well.
Definition: Momentum
\[\overrightarrow p \equiv m \overrightarrow v\nonumber \]
It turns out that if we do happen to have a collection of particles, each with their own individual momentum, then computing the collective momentum \(\overrightarrow p_{cm}\) is a simple matter of summing the individual momenta:
\[\vec p_1+\vec p_2 + \dots = m_1\vec v_1+m_2\vec v_2+\dots=\left(m_1+m_2+\dots\right)\frac{m_1\vec v_1+m_2\vec v_2+\dots}{\left(m_1+m_2+\dots\right)}=M_{tot}\vec v_{cm}\]
Equation 4.1.3 is known as the impulse-momentum theorem . Like kinetic energy, momentum is related to the motion of the object (and the mass), but besides being a different function of mass and velocity than kinetic energy, it is also different in that momentum is a vector while kinetic energy is not. This means that the total impulse can lead to a change in the magnitude or direction (or both) of the momentum vector.
The astute reader will undoubtedly realize that all we have really done here is to introduce a new vector, and use it to repackage Newton's 2nd law. Indeed, we can rewrite the 2nd law thus: \[ \overrightarrow F_{net} = m \overrightarrow a_{cm} = m \dfrac{d}{dt}\overrightarrow v_{cm} = \dfrac{d}{dt}\left(m\overrightarrow v_{cm}\right) = \dfrac{d}{dt}\overrightarrow p_{cm} \]
The Link to Internal Energy
Given that we are making comparisons of work with impulse and momentum with kinetic energy, it is useful to point out a direct mathematical relationship, which not only points out the difference between the two quantities, but will also be quite useful later on. For an individual particle we have:
Two pairs of identical blocks on identical springs are side-by-side as shown in the diagram below. They are set into motion such that just as they reach their (equal) maximum displacements toward each other, they barely come into contact (there is no collision – their springs stop them just as they touch). When they contact, one of the blocks is transferred to the other, and their motion continues.
- Analysis
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Let's start by defining two separate systems here: One that includes the left spring and the blocks it is moving, and one that includes the right spring and the block(s) it is moving. At the moment the blocks touch, all of the potential energy of both systems is stored in the stretch of their respective springs. Losing or adding a block has no effect on this energy, because at the time of the exchange the blocks are not moving, and therefore have no kinetic energy.
So the left side has the same total energy with three blocks as it previously had with two blocks, and the right side has the same total energy that it started with as well. What does that tell us about how the motions of the two systems change, if at all, after the block exchange? We can start by asking about the maximum speeds the blocks attain on each side, before and after. First of all, this occurs when the spring reaches its equilibrium position, because at that moment the potential energy is as low as it can be. Both before and after, this maximum kinetic energy is the same, but the masses are different, so the speeds will not be the same. In order for the kinetic energy to be the same with three blocks as with two, the ratio of the velocities must be:
\[\begin{array}{l} \text{left spring:} && \frac{1}{2}\left(2m\right)v_{\text{max before}}^2=\frac{1}{2}\left(3m\right)v_{\text{max after}}^2 && \Rightarrow && v_{\text{max after}}=\sqrt{\frac{2}{3}}\;v_{\text{max before}}\\ \text {right spring:} && \frac{1}{2}\left(2m\right)v_{\text{max before}}^2=\frac{1}{2}\left(1m\right)v_{\text{max after}}^2 && \Rightarrow && v_{\text{max after}}=\sqrt{2}\;v_{\text{max before}} \end{array}\nonumber\]
Note that this means that the left side is moving slower overall than the right side, and they will not complete a full cycle at the same time. Even though each side will reach far enough at their maximum spring stretched for the blocks to once again touch, the motions are no longer synchronized, so the blocks will not touch again.
One can also compare the momentum of the left side blocks at the equilibrium point to the momentum of the right side blocks at their equilibrium point. The kinetic energies are the same, so since the left side has 3 times the mass, we have:
\[\text{at equilibrium: }{KE}_{\text{left}}={KE}_{\text{right}}\;\;\;\Rightarrow\;\;\;\frac{p_{\text{left}}^2}{2\left(3m\right)}=\frac{p_{\text{right}}^2}{2\left(1m\right)}\;\;\;\Rightarrow\;\;\;p_{\text{left}}=\sqrt{3}\;p_{\text{right}}\nonumber\]
Consider now a collection of particles, each with their own momentum (for simplicity, we will assume that the collection is an ideal gas – the particles are not interacting with each other). Above, we showed that the total momentum of the collection is just the sum of the momenta of the individual particles. But in the previous chapter, we found that the sum of the individual particle kinetic energies is not equal to the collection's (center of mass) kinetic energy. This is easiest to see in the center of mass reference frame. In this frame, \(\vec v_{cm}=0\), which means that the collection's total momentum is zero. But the individual particles can be moving in this frame, so the sum of their kinetic energies is not zero. The difference between adding kinetic energies and momenta is that the kinetic energy of every particle is positive , but momentum vectors of multiple particles add like vectors, and can cancel to zero.
The short summary of this is that in the center of mass frame there is zero momentum for the collection, but there is still non-zero internal energy. Let's see how it works mathematically with a simple two-particle system, like we discussed in Section 3.2 . We start by defining the momentum of the particle as \(\vec p_1\) and \(\vec p_2\). The total momentum of the two-particle collection is just the sum of these:
\[\vec p_{cm} = \vec p_1+\vec p_2\]
The total energy of this group of particles is just the sum of their kinetic energies:
\[E_{tot} = \dfrac{p_1^2}{2m_1}+\dfrac{p_2^2}{2m_2}\]
The kinetic energy of the group (defined in terms of its total mass and center-of-mass speed) is:
\[KE=\dfrac{p_{cm}^2}{2\left(m_1+m_2\right)}=\dfrac{\left(\vec p_{cm}\cdot \vec p_{cm}\right)}{2\left(m_1+m_2\right)}=\dfrac{\left(\vec p_1+\vec p_2\right)\cdot\left(\vec p_1+\vec p_2\right)}{2\left(m_1+m_2\right)}=\dfrac{\left(p_1^2+p_2^2+2\vec p_1\cdot\vec p_2\right)}{2\left(m_1+m_2\right)}\]
The internal energy is the total energy minus the group's (center of mass) kinetic energy, so using the last two equations we get, after some algebra:
\[E_{int} = E_{tot} - KE = \frac{1}{2\left(m_1+m_2\right)}\left[\frac{m_2}{m_1}p_1^2+\frac{m_1}{m_2}p_2^2-2\vec p_1\cdot\vec p_2\right]\]
The general features of this equation match what we already know about internal energy for a two-particle combination. For example, if the particles are moving in the same direction, then they are moving slower in the center of mass frame, and the internal energy is smaller than if they happened to be moving the same speeds toward each other. This fact is reflected in the last term above – if \(\vec p_1\) and \(\vec p_2\) are pointing in the same direction, then the dot product is positive, and the minus sign indicates that the internal energy is reduced. If the two momentum vector directions are in opposite directions, then the dot product is negative, and the last term increases the internal energy.
One thing that is not obvious is whether this equation allows for a negative internal energy for some choice of momentum vectors. This is of course impossible physically, as the smallest the internal energy can be is zero, when the particles are stationary relative to each other. Let's check this in the following way: Start with one particle having a momentum of \(\vec p_1\), and then let the internal energy be a function of the momentum \(\vec p_2\) that we choose for the second particle. Then minimize the internal energy function with respect to this variable. Obviously the minimum will occur when the negative term is as large as possible, and this occurs when \(\vec p_1\cdot\vec p_2 = p_1p_2\), so we have:
\[E_{int}\left(p_2\right) = \frac{1}{2\left(m_1+m_2\right)}\left[\frac{m_2}{m_1}p_1^2+\frac{m_1}{m_2}p_2^2-2p_1p_2\right]\]
Taking a derivative of this function with respect to \(p_2\) (remember, \(p_1\) was selected at the beginning, so it is not varying) and setting it equal to zero gives:
\[0=\frac{dE_{int}}{dp_2} = \frac{1}{2\left(m_1+m_2\right)}\left[2\frac{m_1}{m_2}p_2-2p_1\right]\;\;\;\Rightarrow\;\;\;\frac{m_1}{m_2}p_2=p_1\]
Noting that \(\frac{p}{m}=v\), this result gives that the internal energy is a minimum when \(v_1=v_2\) – both particles moving at the same speed in the same direction. We can confirm by plugging this back in that this gives us the expected result of zero internal energy, so indeed it can never be negative.
Systems and Momentum Conservation
Let's return to following the trajectory of our discussion of work-energy, by revisiting the notion of a system. As before, we define a system as an arbitrarily-grouped collection of objects (which themselves can have internal energies), that can experience forces between themselves, or from outside the system. Previously we said that forces between objects within the system were responsible for internal work and forces exerted on objects within the system from outside provide external work. We will now similarly define internal impulse as coming from forces between objects within the system, and external impulse as coming from objects outside the system.
When it comes to forces between objects within our defined system, we know that the work done on one object does not cancel the work done on the other object. If the internal force is conservative, then the non-zero total work done between the objects can be accounted-for through a change of potential energy. If the internal force is non-conservative, then the non-zero total work done between the objects can be accounted-for through a change of thermal energy. Is there an analogous process for impulse?
To answer this question, we need to determine whether impulses internal to a system don't cancel out, as in the case of work. We again start with Newton's 3rd law, which ensures that the two forces involved in creating the pair of impulses are equal-and-opposite. Impulse vectors have the same directions as their associated force vectors, so the 3rd law pair of forces results in a pair of impulses that are in opposite directions. But what about the magnitudes? Well, the force magnitudes are equal thanks to the third law, so all that remains is the time interval. There is never a moment when a force is acting that its third law pair isn't also acting, so the time intervals are the same. This leads to the following very important result: All of the impulses internal to a system cancel each other out . This means that there is no momentum analog to potential or thermal energy within a system. There is only momentum, and if the system experiences no external impulses, then momentum is conserved for the system. Comparing to what we got for energy, it looks like this:
\[\begin{array}{c} \textbf{work-energy}&\;\;\;\;\;\;&\textbf{impulse-momentum} \\ W_{ext} = \Delta KE \underbrace{- W_{cons} - W_{non - cons}}_{from\;internal\;forces}&\;\;\;\;\;\;&\overrightarrow J_{ext} = \Delta \overrightarrow p_{cm} \underbrace { - \overrightarrow J_{cons} - \overrightarrow J_{non - cons}}_{from\;internal\;forces} \\ W_{ext} = \Delta KE + \Delta PE + \Delta E_{thermal}&\;\;\;\;\;\;&\overrightarrow J_{ext} = \Delta \overrightarrow p_{cm} + 0 \;\;\;\; + \; 0\;\;\;\;\;\;\;\;\;\;\; \end{array}\]
There are two important features of this result:
- It doesn't matter what forces are acting internally . The result we obtained made no mention of whether the internal force was conservative or non-conservative – all forces satisfy Newton's third law, and the pairs act for equal periods of time, so the impulses cancel regardless of the nature of the force.
- The quantity (momentum) that is conserved within the closed system is a vector . This means that adding up all of the momentum vectors of a system at one point in time, then doing so again at another point in time, will give the same total vector in both cases, if the system is isolated from external impulses. This means that the total magnitude and direction don't change, or equivalently that the components measured in a given coordinate system don't change.
Conceptual Question
Two blocks of different masses are attached to identical springs that are horizontal to the frictionless surface on which the block rests. If the springs are compressed the same distance and the blocks are released from rest, how do the following quantities compare for the two blocks when they reach the equilibrium point?
- kinetic energy
- momentum
- velocity
- Solution
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a. The springs are stretched an equal amount, which means they both store the same potential energy. That means that when they get to the equilibrium point where they both have zero potential energy, they must have the same kinetic energy, since the mechanical energy is conserved.
b. We can determine the difference in momenta for the two blocks in two ways. First, we can consider the impulse given to each block by the spring. In the case of the more massive block, the spring force will accelerate it less, which means it will take longer to get to the equilibrium point. At every point during their journeys, the two blocks experience the same amount of force, but since the time interval for the heavier block is longer, it must experience the greater impulse. Therefore the heavier block gains more momentum, and since both blocks started with zero momentum, the heavier block must have more momentum at the equilibrium point. The second solution is much simpler: We already know that the two blocks end with the same \(KE\), so since \(KE=p^2/2m\), the block with the greater mass must have more momentum.
c. With the same kinetic energy, using \(KE=\frac{1}{2}mv^2\), we see that the block with the greater mass must have the lower velocity.
The moral of this story: Although we tend to use kinetic energy, momentum, and velocity as proxies for motion, they are all quite different quantities.
Partial Momentum Conservation
We have to give some extra thought to what we mean by a conserved vector. Since a vector has both magnitude and direction, then to be conserved, both of those properties must remain unchanged. An equivalent way of saying this is that for the vector to be conserved, every component of that vector must be individually conserved. If the full momentum vector is not conserved, it is still possible for one or two of its components to be conserved, if the components of the external impulse in those directions is zero. So for example, a projectile (with no air resistance) conserves momentum in the two horizontal directions, but not in the vertical direction. This allows us to use momentum conservation to solve a much broader range of problems than if we can only consider complete momentum conservation.


3.2: Grades and t-shirts- ranked data
Ranked (or ordinal ) data do not come directly from measurements and do not easily correspond to numbers.
For example, quality of mattresses could be estimated with some numbers, from bad (“0”), to excellent (“5”). These assigned numbers are a matter of convenience. They may be anything. However, they maintain a relationship and continuity. If we grade the most comfortable one as “5”, and somewhat less comfortable as “4”, it is possible to imagine what is “4.5”. This is why many methods designed for measurement variables are applicable to ranked data. Still, we recommend to treat results with caution and keep in mind that these grades are arbitrary.
By default, R will identify ranked data as a regular numerical vector. Here are seven employees ranked by their heights:
Code \(\PageIndex{1}\) (R):
Object rr is the same numerical vector, but numbers “1”, “2” and “3” are not measurements, they are ranks, “places”. For example, “3” means that this person belongs to the tallest group.
Function cut() helps to make above three groups automatically:
Code \(\PageIndex{2}\) (R):
Result is the ordered factor (see below for more explanations). Note that cut() is irreversible operation, and “numbers” which you receive are not numbers (heights) you start from:
Code \(\PageIndex{3}\) (R):
Ranked data always require nonparametric methods. If we still want to use parametric methods, we have to obtain the measurement data (which usually means designing the study differently) and also check it for the normality. However, there is a possibility to re-encode ranked data into the measurement. For example, with the appropriate care the color description could be encoded as red, green and blue channel intensity.
Suppose, we examine the average building height in various cities of the world. Straightforward thing to do would be to put names of places under the variable “city” (nominal data). It is, of cause, the easiest way, but such variable would be almost useless in statistical analysis. Alternatively, we may encode the cities with letters moving from north to south. This way we obtain the ranked data, open for many nonparametric methods. Finally, we may record geographical coordinates of each city. This we obtain the measurement data, which might be suitable for parametric methods of the analysis.


6.5: Eulerization and the Chinese Postman Problem
Not every graph has an Euler path or circuit, yet our lawn inspector still needs to do her inspections. Her goal is to minimize the amount of walking she has to do. In order to do that, she will have to duplicate some edges in the graph until an Euler circuit exists.
Eulerization is the process of adding edges to a graph to create an Euler circuit on a graph. To eulerize a graph, edges are duplicated to connect pairs of vertices with odd degree. Connecting two odd degree vertices increases the degree of each, giving them both even degree. When two odd degree vertices are not directly connected, we can duplicate all edges in a path connecting the two.
Note that we can only duplicate edges, not create edges where there wasn’t one before. Duplicating edges would mean walking or driving down a road twice, while creating an edge where there wasn’t one before is akin to installing a new road!
For the rectangular graph shown, three possible eulerizations are shown. Notice in each of these cases the vertices that started with odd degrees have even degrees after eulerization, allowing for an Euler circuit.
In the example above, you’ll notice that the last eulerization required duplicating seven edges, while the first two only required duplicating five edges. If we were eulerizing the graph to find a walking path, we would want the eulerization with minimal duplications. If the edges had weights representing distances or costs, then we would want to select the eulerization with the minimal total added weight.
Eulerize the graph shown, then find an Euler circuit on the eulerized graph.
- Answer
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This graph can be eulerized by duplicating the edge BC, as shown. One possible Euler circuit on the eulerized graph is ACDBCBA
Looking again at the graph for our lawn inspector from Examples 1 and 8, the vertices with odd degree are shown highlighted. With eight vertices, we will always have to duplicate at least four edges.
Solution
In this case, we need to duplicate five edges since two odd degree vertices are not directly connected. Without weights we can’t be certain this is the eulerization that minimizes walking distance, but it looks pretty good.
The problem of finding the optimal eulerization is called the Chinese Postman Problem, a name given by an American in honor of the Chinese mathematician Mei-Ko Kwan who first studied the problem in 1962 while trying to find optimal delivery routes for postal carriers. This problem is important in determining efficient routes for garbage trucks, school buses, parking meter checkers, street sweepers, and more.
Unfortunately, algorithms to solve this problem are fairly complex. Some simpler cases are considered in the exercises.


9.4: Germany- “The Song of the Germans”
While “The Star-Spangled Banner” traced a long path to its status as national anthem, the process was fairly straightforward. The same cannot be said of many other countries. The current national anthem of Germany is titled “The Song of the Germans” (German: Das Lied der Deutschen ). However, it was not the first national anthem, and it has not been in continuous use. Its history offers an excellent example of how transformations in the identity, contents, and use of an anthem can reflect the complex political journey of an individual nation.
Although it traces its history back for many centuries, the modern nation of Germany came into existence in 1871. By this time, it was typical for European nations to adopt national anthems, and the Germans were certainly not to be excluded from this practice. At first, they adopted the Prussian national anthem. They did so to symbolize the unification of previously- independent Prussian principalities under a single nation. The title of the anthem was “Hail to Thee in the Victor’s Crown,” and it featured the refrain “Hail to thee, emperor!” The melody, however, was that to which “God Save the Queen” is currently sung—a sign of the close ties between European monarchies.
World War I, in which Germany was defeated, prompted major political reorga- nization. The emperor abdicated in 1918 and was replaced by a constitutional government known as the Weimar Republic. The new government required a new anthem—but the song selected for the role was in fact very old. The words to “The Song of the Germans” were written in 1841 by August Heinrich Hoffmann von Fallersleben, a Prussian academic. The text was initially subversive. Fallersleben lived and worked in a monarchy, but his song called for the unification of the German-speaking lands under democratic rule. During his own time, this was a dangerous message, and Fallersleben was dismissed from his post for promoting it. Following the unification of Germany, however, the call became patriotic and Fallersleben’s song was celebrated.
Like Key, Fallersleben wrote his text to fit a preexisting melody. Because he was making a political plea, he selected a political tune: the national anthem of the Austro-Hungarian Empire, which carried a text entitled “God Save Emperor Francis.” By rewriting this important anthem, Fallersleben sought to rewrite political reality. The tune, incidentally, had been composed in 1797 by one of the most important of all Austrian composers, Franz Joseph Haydn. It would continue to serve as the national anthem of Austria, although with different texts to suit changes in government, until World War II.
World War II also brought changes to Germany, which was divided at the close of the war into East Germany and West Germany. The government of East Germany commissioned an entirely new anthem, entitled “Risen from the Ruins,” while West Germany ceased to use an anthem altogether. Although unusual, it is not difficult to explain this development. Anthems tend to represent patriotic feeling and pride in one’s country—sentiments that seemed inappropriate in a post- Holocaust Germany. Various songs— including Ludwig van Beethoven’s
Beethoven’s “Ode to Joy” is the official anthem of the European Union. Here it has been recorded with the original German text, but it is also sung in other languages and performed as a textless instrumental.
“Ode to Joy,”2 now the anthem of the European Union—were used to mark state occasions in West Germany, but “The Song of the Germans” was not officially readopted until 1952.
When it did enter back into use, it was accompanied by significant conflict over the text. The first stanza in particular had become controversial. It opens with the line, “Germany, Germany above all, above all in the world.” To Fallersleben, this meant that the promise of a united German nation must be held above the petty interests of minor German monarchs. To the Nazis, however, it was a call for Germany to take over the world. The second verse, which celebrates German women, wine, and song, perhaps lacks the dignity required of an anthem. After the war, therefore, the third verse was favored:
Unity and justice and freedom For the German fatherland!
Towards these let us all strive Brotherly with heart and hand! Unity and justice and freedom Are the safeguards of fortune;
Flourish in the radiance of this fortune, Flourish, German fatherland!
Controversy over the words, however, has come to stand in for larger political battles. In this way, “The Song of the Germans” simultaneously unites and divides the country, while embodying its difficult past.
Performing “The Song of the Germans”
To consider “The Song of the Germans”3 in use, we will look at a performance that is, in most respects, very similar to Houston’s rendition of “The Star-Spangled Banner.” This performance also took place at a major sporting event—a match between two teams in the national German soccer league. The anthem was again sung by a popular performer. Namika, who was born Hanan Hamdi to Moroccan immigrant parents, is a well-known singer and rapper who has landed several hits since 2015. Like Houston, she performs the anthem in her own individual style. She introduces melodic ornaments but makes a conscious effort not to distract from the dignity of the text. And, finally, the orchestration of the accompaniment is remarkably similar, for Namika is also backed by the militaristic combination of brass and snare drums, and her rendition is likewise punctuated by trumpet fanfares.
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“The Song of the Germans” Composer: Franz Joseph Haydn 3. Lyricist: August Heinrich Hoffmann von Fallersleben Performance: Namika at Bundesliga match between FC Bayern Muenchen and Bayer 04 Leverkusen in Munich (2017) |
There is, however, one very significant difference: Namika is joined by the fans, whose voices can clearly be heard throughout the performance. While Houston was admired as a soloist, Namika is leading a sing-along. Why this difference? It is certainly not the case that Germans are more patriotic or more musical. The German anthem, however, is considerably more singable than “The Star-Spangled Banner.” Given that it outlines a range of only an octave and that the melody is largely conjunct , containing few large melodic leaps, “The Song of the Germans” can be sung by an untrained musician. It is likely that these musical differences have contributed to contrasting cultural traditions: Germans join in, while American leave anthem singing up to the professionals.


15.14: Levels and Types of Control
- Differentiate between strategic, operational, and tactical controls.
- Differentiate between top-down, objective, and normative control.
Strategic Control
Managers want to know if the company is headed in the right direction and if current company trends and changes are keeping them on that right path. To answer this question requires the implementation of strategic control. Strategic control involves monitoring a strategy as it is being implemented, evaluating deviations, and making necessary adjustments.
Strategic control may involve the reassessment of a strategy due to an immediate, unforeseen event. For example, if a company’s main product is becoming obsolete, the company must immediately reassess its strategy.
Implementing a strategy often involves a series of activities that occur over a period. Managers can effectively monitor the progress of a strategy at various milestones, or intervals, during the period. During this time, managers may be provided information that helps them determine whether the overall strategy is unfolding as planned.
Strategic control also involves monitoring internal and external events. Multiple sources of information are needed to monitor events. These sources include conversations with customers, articles in trade magazines and journals, activity at trade conferences, and observations of your own or another company’s operations. For example, Toyota gives tours of its plants and shares the “Toyota Way” even with competitors.
The errors associated with strategic control are usually major, such as failing to anticipate customers’ reaction to a competitor’s new product. BlackBerry had a strong position in the business cell phone market and did not quickly see that its business customers were switching to the iPhone. BlackBerry could not recover.
Operational Control
Operational control involves control over intermediate-term operations and processes but not business strategies. Operational control systems ensure that activities are consistent with established plans. Mid-level management uses operational controls for intermediate-term decisions, typically over one to two years. When performance does not meet standards, managers enforce corrective actions, which may include training, discipline, motivation, or termination.
Unlike strategic control, operational control focuses more on internal sources of information and affects smaller units or aspects of the organization, such as production levels or the choice of equipment. Errors in operational control might mean failing to complete projects on time. For example, if salespeople are not trained on time, sales revenue may fall.
Tactical Control
A tactic is a method that meets a specific objective of an overall plan. Tactical control emphasizes the current operations of an organization. Managers determine what the various parts of the organization must do for the organization to be successful in the near future (one year or less).
For example, a marketing strategy for a wholesale bakery might be an e-commerce solution for targeted customers, such as restaurants. Tactical control may involve regularly meeting with the marketing team to review results and would involve creating the steps needed to complete agreed-upon processes. Tactics for the bakery strategy may include the following:
- building a list of local restaurants, hotels, and grocery stores
- outlining how the bakery website can be used to receive orders
- personally visiting local executive chefs for follow-up
- monitoring the response to determine whether the sales target is met
Strategic control always comes first, followed by operations, and then tactics. For example, a strategy to be environmentally responsible could lead to an operations decision to seek Leadership in Energy and Environmental Design (LEED) certification. This is a program that awards points toward certification for initiatives in energy efficiency, such as installing timed thermostats, using occupant sensors to control lighting use, and using green cleaning products. The tactical decision is deciding which energy-efficient equipment to purchase. At each level, controls ask if the decisions serve the purpose: actual energy savings, the LEED certification, and acting responsibly for the environment.
Top-Down Controls
Top-down controls are also known as bureaucratic controls. Top-down control means the use of rules, regulations, and formal authority to guide performance. It includes things such as budgets, statistical reports, and performance appraisals to regulate behavior and results. Top-down control is the most common process, where senior executives make decisions and establish policies and procedures that implement the decisions. Lower-level managers may make recommendations for their departments, but they follow the lead of senior managers.
Advantages
With top-down control, employees can spend their time performing their job duties instead of discussing the direction of the company and offering input into the development of new policies. Senior executives save time by not explaining why some ideas are used and not others. Heavily regulated businesses may find this approach to be most beneficial.
Disadvantages
The top-down approach has its drawbacks. The lower levels of a company are in touch with customers and recognize new trends or new competition earlier than senior management. A heavy-handed top-down approach may discourage employees from sharing information or ideas up the chain of command.
Objective and Normative Control
Objective control is based on facts that can be measured and tested. Rather than create a rule that may be ambiguous, objective controls measure observable behavior or output. As an example of a behavioral control, let’s say that a store wants employees to be friendly to customers. It could make that a rule as stated, but it may not be clear what that means and is not measurable. To make that goal into an objective control, it might specify, “Smile and greet anyone within 10 feet. Answer customer questions.”
Output control is another form of objective control. Some companies, such as Yahoo, have relaxed rules about work hours and focus on output. Because programmers’ output can be measured, this has worked well, whether an employee works the traditional 9 a.m. to 5 p.m. or starts at noon and works until 8 p.m.
Normative controls govern behavior through accepted patterns of action rather than written policies and procedures. Normative control uses values and beliefs called norms, which are established standards. For example, within a team, informal rules make team members aware of their responsibilities. The ways in which team members interact are developed over time. Team members come to an informal agreement as to how responsibilities will be divided, often based on the perceived strengths of each team member. These unwritten rules are normative controls and can powerfully influence behavior.
Normative control reflects the organization’s culture, the shared values among the members of the organization. Every organization has norms of behavior that workers need to learn. One company may expect employees to take the initiative to solve problems. Another may require a manager’s approval before employees discuss changes outside the department. Some topics may be off-base, while others are freely discussed. Companies will have a mix of controls—top-down, objective, and normative.
Contributors and Attributions
- Levels and Types of Control. Authored by : Talia Lambarki and Lumen Learning. License : CC BY: Attribution
- Image: Chess board. Authored by : Devanath. Located at : https://pixabay.com/en/chess-figure-game-play-board-1215079/ . License : CC0: No Rights Reserved
- Image: Analytics. Authored by : Pexels. Located at : https://pixabay.com/en/analysis-analytics-business-chart-1841158/ . License : CC0: No Rights Reserved
- Image: Top down. Authored by : MovGP0. Located at : https://commons.wikimedia.org/wiki/File:Top_down.svg . License : CC BY-SA: Attribution-ShareAlike


5.1: Reading- The Internet Basics
Introduction
The Internet is probably the most exciting, the most popular, most visible and definitely the “coolest” information systems development of the decade.
What is the Internet?
The origins of the Internet can be found in the early sixties, when the U.S. Department of Defense sponsored a project to develop a telecommunications network that would survive a nuclear attack. It had to link together a diverse set of computers and work in a decentralized manner so that, if any part of the network were not functioning, network traffic would automatically be re-routed via other network nodes. This project quickly grew into a popular academic network linking virtually all major research institutions and U.S. universities. Soon other countries jumped onto the bandwagon, thus linking academics and researchers across the globe. True to the academic ethos, it quickly became a means for global information sharing. By now, businesses also got a piece of the action. This was spurred on by the trend to network the personal computers in home and business environments and the development of more user-friendly, graphical interfaces: the web-browser and the Windows operating system.
The Internet (or, more colloquially, the Net) consists of a huge and fast-growing number (hundreds of thousands) of interconnected networks linked together. Currently more than 100 million users are connected to the Internet. The popularity of the Internet can be explained by the amount of information it makes available: the equivalent of many libraries of information is stored on millions of computers (Internet hosts), much of it free of charge to all Internet users. This information is provided by educational institutions, governmental agencies and organizations, individuals, and increasingly by businesses. Hence, the Internet is frequently referred to as the Information Highway or the Infobahn.
But the Internet is more than just a huge information resource. Its initial purpose was to act as a communications network and it fulfills that role well. It is the transport mechanism for electronic mail, the transfer of computer files, remote computer access and even allows for voice calls. Businesses quickly realized the potential of the multimedia-enabled Internet for marketing purposes. Of late, more and more business transactions are being conducted via the Internet: electronic commerce (e-commerce) is the latest revolution to be embraced by the Internet community.
Electronic mail
Probably the most popular Internet service is electronic mail, more commonly known as email. This consists of the sending of messages composed on the computer, via a network, directly to the computer of the recipient who reads the message on his/her computer. Knowledge workers with access to e-mail write five to ten times as many e-mail messages as hand-written notes. The following are just some of the advantages of e-mail. ·
- Reliability: although there is no guarantee, you will normally receive quick feedback if the address does not exist or there is a similar delivery problem. ·
- Efficiency: many short-cut tools exist to increase your efficiency when composing messages. You can use your computer’s cut-and-paste function, you can have managed address books and lists, when replying to another message you can automatically incorporate any part of the message to which you are, etc. And it is just as easy to send a message to one as to a whole list of addressees. (Admittedly, this results in a lot of abuse and information overload on the recipient’s side.)
- Digital: e-mail is composed on a computer and remains in computer-readable format all the way to its destination. Thus one can also easily incorporate other computer data such as graphics or document files.
- Cheap: because the capacity of the Internet and disk storage is increasing all the time, the cost of a sending and storing a one-page e-mail message is negligible.
- Speed: messages are generally delivered across the world in a matter of seconds.
The e-mail address
Just like with ordinary postal mail (now usually referred to as snail-mail), you need to know the recipient’s address before you can send your message. Internet e-mail addresses have a standard format: username@domain. The username is often the name that your addressee uses to connect to the network, e.g. “jvanbelle” or sometimes a long number. This username is allocated by the LAN administrator. The domain identifies the file server, which acts as the local post office for your recipient’s e-mail. The domain consists of several parts, separated by full stops or dots. The international standard for domain identification is ….
- The country code is the international two-letter code for the country (e.g., au for Australia, za for South Africa, sa for Saudi-Arabia, uk for Great Britain, etc).
- The two most common types of organizations are co for a commercial organization and ac for an academic institution . Less frequent are org for (not-for-profit) organizations, mil for military, net for networks and gov for government agencies.
- Each country has a national Internet naming body that allows its organizations to chose their own name, as long as no one has claimed the same name before. Examples of South African domain names are anc.org.za, uct.ac.za, fnb.co.za.
- Large organizations often refine the domain further by adding the name of their LAN servers, e.g mail.uct.ac.za.
Examples of possible e-mail addresses are<EMAIL_ADDRESS>(Jane working in the statistics department at the University of Cape Town in South Africa<EMAIL_ADDRESS>(information department at the ANC, a political party) or<EMAIL_ADDRESS>(Joe Soap in the marketing department of British Telekom in the U.K.).
The US Americans, having “invented” the Internet, use a slightly different way for their addresses. They leave off their country code (us) and use com for commercial organization or edu for educational institution. Since the majority of Internet users hail from the US, you will encounter many addresses such as<EMAIL_ADDRESS>or<EMAIL_ADDRESS>.
Netiquette
Just as in any other social interaction environment, there are some rules and guidelines for appropriate social behavior on the Net: Netiquette (etiquette on the Internet). The following are some illustrative examples pertaining primarily to e-mail.
- Shouting, THE PRACTICE OF TYPING ENTIRE SENTENCES IN UPPER CASE, is generally seen as novice (newbie) behavior and frowned upon. Perhaps it stems from the disgust with old teletypes and mainframe terminals that did not have lower-case characters.
- The use of emoticons to indicate the emotive content of a sentence is highly recommended. Typed text does not reveal any body language and a joking remark can easily be interpreted the wrong way. Whenever one writes something in jest or with humorous intent, it is advisable to add an emoticon. An emoticon (an icon indicating emotional content) consists of a series of text characters which are meant to be rotated a quarter turn and represent a laughing 🙂 (i.e. equivalent to J or the smiley) winking 😉 or sad face 🙁
- Flaming is the carrying on of a heated personal emotional debate between two or more individuals on a public Internet forum. A flame war is generally a sign of immature behavior by individuals who cannot take perspective and should really take the discussion off-line.
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Netizens (inhabitants of the Internet i.e. frequent net surfers) often use standard but,
to the non-initiated, cryptic abbreviations. Examples are: BTW = by the way ; ROFL = rolling on the floor with laughter ; TPTB = the powers that be; BRB = Be Right Back. This vocabulary has been adopted and expanded with the growth of Short Message Service (SMS) use on cellular phones.
The Web
The Internet service that has received the most attention from the public media is the WorldWide Web or the Web for short (sometimes also called WWW or W3). The Web is a vast collection of multimedia information located on Web servers attached to the Internet.
Its popularity is due to a number of reasons.
- Information links are transparent. Links to any other piece of information located anywhere on the Internet can be inserted in a web document. A simple click of the mouse takes the reader completely automatically from one Web server to another, quite possibly in another country.
- Information can be presented in a hypertext link format whereby one can jump immediately from one concept to a related concept or explanation. No need to read text in the traditional top-to-bottom sequential way.
- It allows for multimedia information. A Web document can incorporate rich and colourful graphics, animation, video clips, sound etc. Just think of the marketing opportunities!
- The Web supports interactive applications. Web applications can request information from visiting users and documents can include programming instructions. Users can even download small programs (often written in Java) that could perform some processing on the user’s computer or display special visual effects.
Reading or accessing information on the Web is called surfing the Net because one jumps from one hypertext link to another following whatever takes your fancy. In order to surf the Net you need some special browser program that understands the Web protocols and formats and presents the information to suit your computer monitor. You also need an access point or connection to the Internet. Your Internet connection may be automatic if your computer is connected to a (corporate) LAN that connects directly to the Internet, or it may be by means of a special subscription to a business that specializes in providing Internet access for others: the Internet Service Provider (ISP). Access to the ISP for individual users is usually via a dial-up connection i.e. using a modem and telephone.
Once a newbie (new user) is connected to the Internet (online), she faces the daunting task of finding her way amongst the huge variety of information offered. The easiest way in is usually by means of a search engine: a Web site that tries to catalogue the information available on the Internet. By entering one or more search words, the engine will provide you with a couple of adverts and a list of documents that contain the word(s) for which you are looking.
All information on the Web is uniquely identified by the URL (Uniform Resource Location), which is really the full Internet address of a Web document. The URL consists again of the Web server’s domain address, followed by the access path and file name on the server. Examples of URLs are www.hotbot.com/sports/main.html (the main page on the sports section of the HotBot search engine) or http://www.commerce.uct.ac.za/informationsystems/ (containing details about UCT’s department of information systems). Note the similarities and differences between an URL and an e-mail address.
Other Internet services
A number of other services are available on the Internet. The Usenet consists of ongoing discussion fora (or newsgroups) on an extremely wide variety of topics, from forensic psychology to Douglas Adams, from Star Trek to cryptography. The discussion happens entirely by means of e-mail and, when you subscribe to a given newsgroup, you can browse through the contributions of the last few days and reply with your own contribution.
More specialized services exist, such as ftp (file transfer protocol) for the transfer of large computer files, and telnet, the remote access of computers elsewhere, but they are used less frequently. In any way, these services are now being performed transparently by most Web browsers. Similarly, older services such as Gopher and Veronica have really been replaced almost entirely by the Web.
Internet protocols and standards
Different computers and networks can communicate via the Internet because a number of basic Internet communication standards have been defined. Any network connected to the Internet will translate its own standards and protocols into those used on the Internet by means of a bridge.
The most fundamental and “lowest level” protocol is the TCP/IP (Transmission Control Protocol/Internet Protocol). This protocol is also the native protocol of computers using the Unix operating system, which explains why Unix computers are so popular as Internet servers.
On top of TCP/IP are the “mid-level” protocols defined for the various Internet services. Perhaps the best known of these is http (Hypertext Transmission Protocol), which specifies how the Web information is made available and transmitted across the Internet. Other protocols and standards are STMP and MIME (for e-mail) or ftp.
Information made available via the Web is usually formatted using a special standard: the Hypertext Markup Language (HTML), which actually consists of plain text files with visual formatting commands inserted between the text. Most desktop productivity software allows you to save your document directly in the HTML format. Special HTML editors allow much finer control over the final layout of your Web document. A later development is Extensible Markup Language (XML), which increases the flexibility of web documents by allowing them to be viewed not only using a web browser, but also on different platforms such as a PDA or cellular telephone.
- Discovering Information Systems Section 6.4. Authored by : Jean-Paul Van Belle, Mike Eccles, and Jane Nash. Located at : https://archive.org/details/ost-computer-science-discoveringinformationsystems . License : CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
- Authored by : geralt. Located at : https://pixabay.com/en/tree-structure-networks-internet-200795/ . License : CC0: No Rights Reserved
- HTML. Authored by : lmonk72. Located at : https://pixabay.com/en/website-code-html-coding-647013/ . License : CC0: No Rights Reserved
- Buenas noticias - email marketing. Authored by : RaHuL Rodriguez. Located at : https://www.flickr.com/photos/rahulrodriguez/9162677329/ . License : CC BY-SA: Attribution-ShareAlike