Verbal and Numerical Expressions of Probability: “It's a Fifty–Fifty Chance”

• Published in: Organizational behavior and human decision processes Vol. 81; no. 1; pp. 115 - 131
• Main Authors: de Bruin, Wändi Bruine, Fischhoff, Baruch, Millstein, Susan G., Halpern-Felsher, Bonnie L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.01.2000; Elsevier; Elsevier Science Publishing Company, Inc
• Series: Organizational Behavior and Human Decision Processes
• Subjects: Behavior; Biological and medical sciences; Cognition. Intelligence; Decision making. Choice; Fundamental and applied biological sciences. Psychology; Probability; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Studies; Uncertainty; United States > US; Human; Uncertainty; School age; Decision making; Reasoning; Adolescent; Young adult; Risk; Information layout; Child; Comparative study; Subjective probability
• ISSN: 0749-5978; 1095-9920
• DOI: 10.1006/obhd.1999.2868

When estimating risks, people may use “50” as an expression of the verbal phrase “fifty–fifty chance,” without intending the associated number of 50%. The result is an excess of 50s in the response distribution. The present study examined factors determining the magnitude of such a “50 blip,” using a large sample of adolescents and adults. We found that phrasing probability questions in a distributional format (asking about risks as a percentage in a population) rather than in a singular format (asking about risks to an individual) reduced the use of “50.” Less numerate respondents, children, and less educated adults were more likely to say “50.” Finally, events that evoked feelings of less perceived control led to more 50s. The results are discussed in terms of what they reveal about how people express epistemic uncertainty.