Contributions to Mathematical Psychology, Psychometrics, and Methodology

Part of the series Recent Research in Psychology pp 375-388

Natural Sampling: Rationality without Base Rates

  • Gernot D. KleiterAffiliated withDepartment of Psychology, University of Salzburg

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The Bayesian classification of single cases into classes is investigated. The neglect of class base rates is usually considered to be a fundamental violation of the principles of rationality and, in human judgment, is called ‘the base rate fallacy’. This paper analyzes an important special sampling condition in which the base rates actually turn out to be irrelevant in estimating classification probabilities. It is shown that the base rates do not affect the precision of the estimates of classification probability. This precision is modeled by a second-order probability distribution. Implications for the design of artificial and for the modeling of natural knowledge systems are discussed.