Adolescents' and adults' understanding of probability expressions

Purpose: To examine whether there are differences between adolescents and a dults in their interpretation of probability terms. Methods: Participants were 20 fifth graders, 54 seventh graders, 45 ninth g raders, and 34 young adults (mean adult age = 26.24 years, standard deviati on = 2.09) from the San Francisco Bay area. They completed a self-administe red survey asking them to assign percentage estimates (0% to 100%) to 30 ra ndomly ordered probability terms. Results: Significant age differences in the mean percentage estimates for 8 of the 30 terms were shown. Moreover, we found large variation in the inte rpretation of most probability terms studied, with larger variation among t he adolescents than adults. Finally, all age groups had some difficulty cor rectly differentiating between "possibly" and "probably." Conclusions: Owing to wide variation in the interpretation of probability t erms, both within and across age groups, we suggest health practitioners us e percentages rather than probability terms to convey risk to both adolesce nts and adults. (C) Society for Adolescent Medicine, 2000.