Self-selection bias is the problem that very often results when survey respondents are allowed to decide entirely for themselves whether or not they want to participate in a survey. To the extent that respondents' propensity for participating in the study is correlated with the substantive topic the researchers are trying to study, there will be self-selection bias in the resulting data. In most instances, self-selection will lead to biased data, as the respondents who choose to participate will not well represent the entire target population.

A key objective of doing surveys is to measure empirical regularities in a population by sampling a much smaller number of entities that represent the whole target population. Modern sampling theory is predicated on the notion that whether an entity is ...