Comprehension of health risk probabilities: the roles of age, numeracy, format, and mental representation

Abstract

Probabilities, an essential dimension of risk communication, can be presented in various formats including frequencies (e.g., 1 in 10), percentages (e.g., 10%), or verbal phrases (e.g., unlikely); the literature is mixed concerning which format best supports comprehension. Additionally, it is not well understood how people who vary in their level of numeracy understand those probabilities. The goal of the present three-phase within-participant study was to understand how the factors of format and numeracy influence comprehension and mental representations of probabilities for younger and older adults. Overall, the results of this research clearly indicated that comprehension and mental representation of health risk probabilities are influenced by format, age, and numeracy. To best support comprehension and comparison of health risk probabilities for younger adults and healthy older adults with varying numeracy, percent format should be used.