Self-selection bias

In statistics, self-selection bias arises in any situation in which individuals select themselves into a group, causing a biased sample with nonprobability sampling. It is commonly used to describe situations where the characteristics of the people which cause them to select themselves in the group create abnormal or undesirable conditions in the group. It is closely related to the non-response bias, describing when the group of people responding has different responses than the group of people not responding.

Self-selection bias is a major problem in research in sociology, psychology, economics and many other social sciences.^[1] In such fields, a poll suffering from such bias is termed a self-selected listener opinion poll or "SLOP".^[2] The term is also used in criminology to describe the process by which specific predispositions may lead an offender to choose a criminal career and lifestyle.

While the effects of self-selection bias are closely related to those of selection bias, the problem arises for rather different reasons; thus there may be a purposeful intent on the part of respondents leading to self-selection bias whereas other types of selection bias may arise more inadvertently, possibly as the result of mistakes by those designing any given study.