title: Adolescents' and adults' understanding of probability expressions.
abstract: OBJECTIVE
  To examine whether there are differences between adolescents and adults in their interpretation of probability terms.
  
  
  METHODS
  Participants were 20 fifth graders, 54 seventh graders, 45 ninth graders, and 34 young adults (mean adult age = 26.24 years, standard deviation = 2.09) from the San Francisco Bay area. They completed a self-administered survey asking them to assign percentage estimates (0% to 100%) to 30 randomly 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 interpretation of most probability terms studied, with larger variation among the adolescents than adults. Finally, all age groups had some difficulty correctly differentiating between "possibly" and "probably".
  
  
  CONCLUSIONS
  Owing to wide variation in the interpretation of probability terms, both within and across age groups, we suggest health practitioners use percentages rather than probability terms to convey risk to both adolescents and adults.
authors.affiliation: Division of Adolescent Medicine, Department of Pediatrics, University of California, San Francisco, San Francisco, California 94143-0503, USA. mbiehl@itsa.ucsf.edu
authors.forename: M
authors.initials: M
authors.lastname: Biehl
authors.forename: B L
authors.initials: BL
authors.lastname: Halpern-Felsher
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000523:psychology*; D000704:Analysis of Variance; D002140:California; D003142:Communication; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D011336:Probability; D000297:Psychology, Adolescent / Q000706:statistics & numerical data; D012309:Risk-Taking