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date: 22 February 2020


A Dictionary of Psychology

Andrew M. Colman

randomization n. 

A technique of particular importance in experimental design, introduced by the English statistician and geneticist Ronald Aylmer Fisher (1890–1962) in an article in the Journal of the Ministry of Agriculture in 1926, in which experimental subjects are assigned to treatment conditions strictly at random in order to control for the influence of extraneous variables and to enable inferential statistics to be used to determine the significance of any effects that are then observed. The control of extraneous variables through random assignment to treatment groups can be demonstrated by choosing a page from a telephone directory, assigning all the entries on it to two groups by tossing a coin, and then comparing the two groups for the number of surnames containing the letter p, or the number of telephone numbers ending in 6, or the number of addresses in a particular sector of the area covered by the directory, or any other characteristic of the entries whatsoever: in each case the two groups will turn out to be roughly similar, especially if the groups are large. See also randomized controlled trial, time sampling diary. [From Old French randon random, from randir to gallop + -izare from Greek -izein to cause to become + Latin -ation indicating a process or condition]