Judgments of and by Representativeness
Technical rept. Jan 1980-Apr 1981
STANFORD UNIV CA DEPT OF PSYCHOLOGY
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The concept of representativeness and the conditions in which it can be used to explain intuitive predictions and probability judgments are discussed. Four cases of representativeness are distinguished that refer to the relations between a value and a variable an instance and a category a sample and a population an effect and a cause. The principles of representativeness differ significantly from the laws of probability. In particular, specificity can increase the representativeness of an event, even though it always reduces its probability. Several studies of judgment are reported in which naive and sophisticated respondents judge a conjunction to be more probable than one of its components. Violations of the conjunction rule. PAB PB, are observed in both between-subjects and within-subjects comparisons, with both fictitious and real-world events. The theoretical and practical implications of the conjunction fallacy are explored.