computer aid to judgmental forecasting

The elicitation of subjective probability as a means of gaining access to an individual's internal state of uncer tainty is a procedure commonly used in decision-aiding techniques (see Wright, 1984). By this means expert judg ment may be tapped. Experimental psychologists have also used this method for exploring the characteristics of human judgment. Judgments expressed as subjective probabilities must conform to the probability laws. However, Tversky and Kahneman (1983) and Wright and Whalley (1983) have shown that actual probabilistic judgments of future event likelihood frequently contradict axioms derived from proba bility theory. In the former study, this contradiction was shown even in judgments given by professional statisti cians. The program described here takes advantage of some axioms of probability theory to enable the user to make coherent judgments of the probability of future events. As incoherent (i.e., axiom-breaking) forecast probabilities cannot be accurate, the program interacts with the user to resolve inconsistencies in a manner that meets with the user's approval. selects a the and is ini