ON PEOPLES UNDERSTANDING OF THE DIAGNOSTIC IMPLICATIONS OF PROBABILISTIC DATA

Two lines of prior research into the conditions under which people see k information are examined in light of two statistical definitions of diagnosticity. Five experiments are reported. In two, subjects selecte d information in order to test a hypothesis. In the remaining three, t hey selected information in order to convince someone else of the trut h of a known hypothesis. A total of 567 university students served as subjects. The two primary conclusions were as follows: (1) When the ta sk is highly structured by the environment, subjects select informatio n diagnostically, and (2) when the task is less structured, so that su bjects must seek relevant information not manifest, they select inform ation pseudodiagnostically. Possible relations to other laboratory inf erence tasks and to clinical judgment are discussed.