Subjective Probability: A Judgment of Representativeness
This paper explores a heuristic — representativeness — according to which the subjective probability of an event, or a sample, is determined by the degree to which it: (i) is similar in essential characteristics to its parent population; and (ii) reflects the salient features of the process by which it is generated. This heuristic is explicated in a series of empirical examples demonstrating predictable and systematic errors in the evaluation of uncertain events. In particular, since sample size does not represent any property of the population, it is expected to have little or no effect on judgment of likelihood. This prediction is confirmed in studies showing that subjective sampling distributions and posterior probability judgments are determined by the most salient characteristic of the sample (e.g., proportion, mean) without regard to the size of the sample. The present heuristic approach is contrasted with the normative (Bayesian) approach to the analysis of the judgment of uncertainty.
KeywordsPosterior Probability Subjective Probability Parent Population Sample Ratio Sample Difference
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- Cohen, J., and Hansel, C.E.M., Risk and Gambling, Philosophical Library, New York. 1956.Google Scholar
- Edwards, W., ‘Conservatism in Human Information Processing’, in B. Kleinmuntz (ed.). Formal Representation of Human Judgment, Wiley, New York, 1968, pp 17–52.Google Scholar
- Extes, W.K., ‘Probability Learning’, in A W Melton (ed.), Categories of Human Learning, Academic Press, New York, 1964, pp. 89–128.Google Scholar
- Feller, W., An Introduction to Probability Theory and Its Applications ( 3rd ed. ). Vol. I, Wiley, New York. 1968.Google Scholar
- Garner, W.R., ‘Good Patterns Have Few Alternatives’, American Scientist 58 (1970), 34–43.Google Scholar
- Pitz, G F., ‘Sample Size, Likelihood, and Confidence in a Decision’, Psychcmomic Science 8 (1967), 257–258.Google Scholar
- Rapoport, A., and Wallsten, T.S., ‘Individual Decision Behavior’. (Vol. 23) in Annual Review of Psychology, Annual Reviews, Palo Alto, 1972, pp. 131–176.Google Scholar
- Vlek, C., ‘The Use of Probabilistic Information in Decision-Making’, Psychological Institute Report No. 009-65, University of Leiden, The Netherlands, 1965.Google Scholar
- Wagenaar, W.A., ‘Subjective Randomnew and the Capacity to Generate Information’, in A.F. Sanders (Ed.), Attention and Performance III, Acta Ptychologica, 33 (1970), 233–242.Google Scholar