Regression towards the mean

A statistical phenomenon in which, upon repeated testing, the mean of the subject group will on the second occasion fall between the group mean when first measured and the population mean – individuals with high or low scores, that is, at the extremes, will tend to move in the direction of the population mean.

(see also: regressive fallacy, Gambler's fallacy, pattern-seeking, Law of large numbers, standard deviation)

Back to: Glossary A-Z