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Abstract We performed two studies to investigate the conditions under which individuals use anecdotal (case history) versus statistical (base rate) information in making judgments. In Study 1, a fictitious (unfamiliar) automobile, the Clipper, was rated after a 2-part essay about it was read that was either an anecdote followed by contradictory statistics or statistics followed by a contradictory anecdote. Statistical information that rendered the anecdote atypical had a great impact, whereas anecdotal information had little. In Study 2, 3 automobiles that varied in prior knowledge and evaluation were rated: Clipper (unfamiliar/neutral), Honda (familiar/positive), and Yugo (familiar/negative). The impact of statistical information on participants' evaluations was great regardless of prior evaluation or familiarity. We propose that the experimental paradigm used provides a good context for studying basic and applied issues relating to people's use of base rate information, and the results indicate that base rate information will be used when it is comprehensible and diagnostically relevant.
Krupat et al. (Tue,) studied this question.