Random selection (sometimes called random sampling) is the way in which a particular subset of a population (i.e., sample) is chosen. For selection to be random, two criteria must be met: (1) the members of a population have an equal statistical probability of being selected for the sample, and (2) the probability of being selected is independent of whether any other member has been selected. This entry compares random selection to nonrandom selection, distinguishes random selection from random assignment, describes several types of random selection, and finally provides basic examples of random selection.

Random selection is a crucial part of most research designs. It determines the participants of the study, which in turn provides the data the researcher uses to draw conclusions. Appropriate use of random ...