Introduction to Sampling
A population consists of all members of a group in which a researcher has an interest. It may be small, such as all psychiatrists affiliated with a particular hospital, or it may be large, such as all high school seniors in a state. When populations are large, researchers usually use a sample. A sample is a subset of a population. For instance, we might be interested in the attitudes of all registered nurses in Texas toward people with AIDS. The nurses would constitute the population. If we administered an AIDS attitude scale to all these nurses, we would be studying the population, and the summarized results (such as averages) would be referred to as parameters. If we studied only a sample of the nurses, the summarized results would be referred to as statistics.