Adolescents' misinterpretation of health risk probability expressions

To determine if differences exist between adolescents and physicians in their numerical translation of 13 commonly used probability expressions (eg, possibly, might). Cross-sectional. Adolescent medicine and pediatric orthopedic outpatient units. 150 adolescents and 51 pediatricians, pediatric orthopedic surgeons, and nurses. Numerical ratings of the degree of certainty implied by 13 probability expressions (eg, possibly, probably). Adolescents were significantly more likely than physicians to display comprehension errors, reversing or equating the meaning of terms such as probably/possibly and likely/possibly. Numerical expressions of uncertainty (eg, 30% chance) elicited less variability in ratings than lexical expressions of uncertainty (eg, possibly). Physicians should avoid using probability expressions such as probably, possibly, and likely when communicating health risks to children and adolescents. Numerical expressions of uncertainty may be more effective for conveying the likelihood of an illness than lexical expressions of uncertainty (eg, probably).