selection bias

Syllable breakdown

Dictionary meaning

a systematic error in epidemiological research arising when the participants included in a study are not representative of the population they are intended to represent, such that the observed results cannot be validly generalised; selection bias can arise at the recruitment stage — when volunteers differ systematically from non-volunteers in ways related to the outcome — at the analysis stage through differential loss to follow-up, or in case-control studies when controls are drawn from a population that does not accurately represent the source population of the cases; healthy worker effect is a classic example in occupational epidemiology where employed populations appear healthier than the general population because severely ill individuals are less likely to be employed; minimising selection bias requires careful attention to sampling frames, recruitment strategies, and retention methods throughout the conduct of a study