Constant

The term constant simply refers to something that is not variable. In statistics, and survey research in particular, responses are typically described as random variables, roughly meaning that the responses cannot be predicted with certainty. For example, when people are asked whether they approve or disapprove of a particular political leader, typically there is uncertainty about what the response will be. As another example, in a survey regarding whether individuals approve or disapprove of the death penalty, responses are not constant simply because some individuals will approve and others will not.

Although at some level, the difference between a constant and a random variable is clear, the distinction between the two often becomes blurred. Consider, for example, the population mean, μ. That is, μ is the ...