Base Rate Effects on the Interpretation of Probability and Frequency Expressions
Abstract
Two studies were run to determine whether the interpretations of statements or forecasts using vague probability and frequency expressions such as likely, improbable, frequently, rarely, were sensitive to the base rates of the events involved. In the first experiment, professional weather forecasters judged situations drawn from a medical context. In the second, students judged matched forecast scenarios of common semantic content that differed only in prior probability (as determined by an independent group of subjects). Results were: (a) The interpretations of forecasts using neutral terms (e.g., possible) and terms above neutral (e.g., usually) were strong, positive functions of base rate, while the interpretations of forecasts using terms below neutral (e.g., rarely) were much less affected by base rates; (b) In the second experiment interpretations of forecasts appeared to represent some kind of average of the meaning of the expression and the base rate. Keywords: Cognitive science, Decision making, Psychometrics.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1988
- Accession Number
- ADA198456
Entities
People
- James A. Cox
- Samuel Fillenbaum
- Thomas S. Wallsten
Organizations
- University of North Carolina at Chapel Hill