Varied measures of contingency have appeared in the psychological judgment literature concerned with binary variables. These measures are examined, and the inappropriateness of some are noted. As well, it is argued that accurate judgments about related variables should not be used to infer that the judgments are based on the appropriate information.A number of studies in the psychological literature have been concerned with judgments of contingency or correlation between two binary variables (Allan & Jenkins, in press;Gray, 1976;Green, Jurd, & Seggie, 1979;Inhelder & Piaget, 1958;Seggie, 1975;Seggie & Endersby, 1972;Smedslund, 1963;. One purpose of the present note is to evaluate the various measures of contingency that have been used in these studies. A second purpose is to argue that accurate judgments about two variables that are related should not be used to infer that the judgments are based on the appropriate information.
MEASUREMENT OF CONTINGENCY OR CORRELATIONConsider the 2by 2 matrix in Figure