APA Dictionary of Psychology

a measure of the strength of the relationship between two dichotomous variables, such as a person’s handedness (left or right) and graduation from college (yes or no). It ranges from −1 to +1, with values close to either negative or positive 1 indicating a very strong relation and values around 0 indicating little to no relation. Also called Yule’s coefficient of association. [George Udny Yule (1871–1951), British statistician]