Measuring Risk Perceptions

Objectives . Risk perceptions are central to good health decisions. People can judge valid probabilities but use 50% disproportionately. The authors hypothesized that 50% is more likely than other responses to reflect not knowing the probability, especially among individuals with low education and numeracy, and evaluated the usefulness of eliciting “don’t know†explanations. Methods . Respondents ( n = 1020) judged probabilities for living or dying in the next 10 years, indicating whether they gave a good estimate or did not know the chances. They completed demographics, medical history, and numeracy questions. Results . Overall, 50% was more likely than other probabilities to be explained as “don’t know†(v. “a good estimate†). Correlations of using 50% with low education and numeracy were mediated by expressing “don’t know.†Judged probabilities for survival and mortality explained as “don’t know†had lower correlations with age, diseases, and specialist visits. Conclusions . When judging risks, 50% may reflect not knowing the probability, especially among individuals with low numeracy and education. Probabilities expressed as “don’t know†are less valid. Eliciting uncertainty could benefit theoretical models and educational efforts.