Coma Overview. A coma is a deep state of unconsciousness in which individuals do not consciously respond to stimuli in their environment. Coma can result from injury such as head trauma, or an underlying illness such as an infection or tumor, or toxins that enter the body. Patients in a coma are unable to think consciously and lack awareness of their surroundings, but they do retain basic life support functions, such as breathing and circulation.
The best known classification is that developed by the psychologist Stanley Smith Stevens, who proposed four levels, or scales, of measurement: nominal, ordinal, interval, and ratio.
Scales of measurement refer to ways in which variables/numbers are defined and categorized. Each scale of measurement has certain properties which in turn determines the appropriateness for use of certain statistical analyses. The four scales of measurement are nominal, ordinal, interval, and ratio. Nominal: Categorical data and numbers that are simply used as identifiers or names represent a nominal scale of measurement. Numbers on the back of a baseball jersey and your social security number are examples of nominal data.