Judging Unlikely Conjunctions
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Date
1985-05
Authors
Fischhoff, Baruch
Journal Title
Journal ISSN
Volume Title
Publisher
Decision Research
Abstract
Several procedures were used to elicit direct numerical estimates
of the probabilities associated with various events created by the
conjunction of three independent subevents. However the question was
asked, many respondents showed a misunderstanding of the conjunction
rule. Less than one half met the minimal criterion of consistently
assigning a probability to the conjunction that was no larger than that
associated with the least likely constituent event. As a result, subjects
as a whole greatly overestimated the conjunctive probability.
When attention was restricted to individuals who had followed the
conjunction rule, a tendency remained to overestimate the smallest
probabilities, relative to the calculated values. Subsidiary results
concerned the effects on judgment of wishful thinking, the similarity of
the constituent events, and the source of the constituent events. The
implications of these results for eliciting and presenting the
probabilities of unlikely events are also discussed.
Description
60 pages
Keywords
conjunctions, unlikely conjunctions, statistics, probability
Citation
Fischhoff, B. (1985). Judging unlikely conjunctions (Report 2, No. 85-2). Eugene, OR: Decision Research.