Verbal and Numerical Expressions of Probability: "It's a Fifty-Fifty Chance"

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. Copyright 2000 Academic Press.

[1]  Dan G. Erwin,et al.  Understanding Risk , 2002, Inf. Secur. J. A Glob. Perspect..

[2]  Refractor.  Uncertainty , 2001, The Lancet.

[3]  M. Biehl,et al.  Adolescents' and adults' understanding of probability expressions. , 2001, The Journal of adolescent health : official publication of the Society for Adolescent Medicine.

[4]  Baruch Fischhoff,et al.  Fifty–fifty = 50%? , 1999 .

[5]  B. Fischhoff,et al.  Adolescent vulnerability: A framework for behavioral interventions , 1998 .

[6]  Lisa M. Schwartz,et al.  The Role of Numeracy in Understanding the Benefit of Screening Mammography , 1997, Annals of Internal Medicine.

[7]  Andrew Hale,et al.  Against the gods: the remarkable story of risk , 1997 .

[8]  S. R. Jammalamadaka,et al.  Against the Gods: The Remarkable Story of Risk , 1999 .

[9]  Jeff Dominitz,et al.  Perceptions of Economic Insecurity: Evidence from the Survey of Economic Expectations , 1996 .

[10]  S. Sloman.  The empirical case for two systems of reasoning. , 1996 .

[11]  R F Nease,et al.  Perceptions of breast cancer risk and screening effectiveness in women younger than 50 years of age. , 1995, Journal of the National Cancer Institute.

[12]  Sandy Gordon,et al.  Breaking the Vicious Circle , 1995 .

[13]  D. Davidson,et al.  The Representativeness Heuristic and the Conjunction Fallacy Effect in Children's Decision Making. , 1995 .

[14]  A. Tversky,et al.  Support theory: A nonextensional representation of subjective probability. , 1994 .

[15]  L. Schauble,et al.  Beyond Modularity: A Developmental Perspective on Cognitive Science. , 1994 .

[16]  Robert S. Lockhart,et al.  Distributional versus singular approaches to probability and errors in probabilistic reasoning , 1993 .

[17]  D. Budescu,et al.  Preferences and reasons for communicating probabilistic information in verbal or numerical terms , 1993 .

[18]  Maria T. Potenza,et al.  The use of judgment heuristics to make social and object decisions: a developmental perspective , 1991 .

[19]  A. H. Murphy,et al.  The expected value of frequency calibration , 1990 .

[20]  I. Erev,et al.  Verbal versus numerical probabilities: Efficiency, biases, and the preference paradox☆ , 1990 .

[21]  R. Gelman.  First Principles Organize Attention to and Learning About Relevant Data: Number and the Animate‐Inanimate Distinction as Examples , 1990 .

[22]  Rochel Gelman,et al.  First Principles Organize Attention to and Learning About Relevant Data: Number and the Animate-Inanimate Distinction as Examples , 1990, Cogn. Sci..

[23]  S. Link,et al.  Bias in Quantifying Judgments , 1989 .

[24]  K. Fiedler.  The dependence of the conjunction fallacy on subtle linguistic factors , 1988 .

[25]  Karl Halvor Teigen,et al.  The language of uncertainty , 1988 .

[26]  R. Keeney,et al.  Improving risk communication. , 1986, Risk analysis : an official publication of the Society for Risk Analysis.

[27]  Robert D. Behn,et al.  Quick Analysis for Busy Decision Makers , 1984 .

[28]  A. Tversky,et al.  Variants of uncertainty , 1982, Cognition.

[29]  A. Tversky,et al.  Intuitive Prediction: Biases and Corrective Procedures , 1982 .

[30]  Averill M. Law,et al.  Simulation Modeling and Analysis , 1982 .

[31]  N. Weinstein.  Unrealistic optimism about future life events , 1980 .

[32]  Seymour Sudman,et al.  Improving Interview Method and Questionnaire Design: Response Effects to Threatening Questions in Survey Research. , 1980 .

[33]  Seymour Sudman,et al.  Improving Interview Method and Questionnaire Design. , 1982 .

[34]  D. Sharp,et al.  Education and cognitive development : the evidence from experimental research , 1979 .

[35]  J. Saltiel.  [Risks of smoking]. , 1978, La Revue du praticien.

[36]  E. Langer.  The Psychology of Chance , 1977 .

[37]  John W. Yolton,et al.  THE EMERGENCE OF PROBABILITY: A Philosophical Study of Early Ideas about Probability, Induction and Statistical Inference , 1976 .

[38]  T. Fine,et al.  The Emergence of Probability , 1976 .

[39]  A. Tversky,et al.  Judgment under Uncertainty: Heuristics and Biases , 1974, Science.

[40]  F. N. David,et al.  Games, gods and gambling: The origins and history of probability and statistical ideas from the earliest times to the Newtonian era , 1963 .

[41]  J B Hurry,et al.  THE BREAKING OF THE VICIOUS CIRCLE , 1913, British medical journal.

[42]  Maximilian b. Arrer.  Ueber die Bedeutung der Convergenz- und Accommodationsbewegungen für die Tiefenwahrnehmung , 1897 .