title: Numeracy and the medical student's ability to interpret data.
abstract: BACKGROUND
  Although the ability to work with numbers is important to the practice of medicine, little is known about physician numeracy (basic skill with numbers).
  
  
  OBJECTIVE
  To test medical students' numeracy and how it relates to the ability to interpret risk-reduction information.
  
  
  METHODS
  Randomized, cross-sectional survey.
  
  
  METHODS
  62 first-year medical students at the University of North Carolina at Chapel Hill medical school who attended a risk-communication seminar and had usable survey data (46% of the 134 students who received the survey).
  
  
  METHODS
  Students were given information about the baseline risk for developing a hypothetical disease and were randomly assigned to one of four risk-reduction presentations-relative risk reduction, absolute risk reduction, number needed to treat (NNT), or a combination of these three formats-about how two drugs would reduce this risk.
  
  
  METHODS
  Number of correct answers to three numeracy questions (stating that 500 heads would be expected in 1000 coin flips; converting "1% of 1000" to 10; and converting "1 in 1,000" to 0.1%). Correct data interpretation was judged with two tasks: a comparative task (i.e., state which drug provides greater benefit) and a quantitative task (i.e., calculate how much one of the drugs reduces disease risk).
  
  
  RESULTS
  77% of students answered all three numeracy questions correctly; 18% answered two correctly; and 5% answered one or none correctly. While 90% correctly stated which drug worked better, only 61% accurately interpreted the quantitative data. The ability to interpret data varied with numeracy: 71% of students who answered all three numeracy questions correctly also accurately interpreted the quantitative data, compared with 36% who answered two questions correctly and 0% who answered one or no questions correctly (P < 0.01). Correct quantitative interpretation was lower with the NNT format than with the other three formats (25% vs. 75%; P = 0.01).
  
  
  CONCLUSIONS
  Almost one quarter of first-year medical students in our study had trouble performing basic numerical tasks. Those who had trouble also seemed to have difficulty interpreting medical data. This difficulty seemed to be exacerbated by presenting data in the NNT format.
authors.affiliation: Division of General Medicine and Clinical Epidemiology, University of North Carolina, Chapel Hill, USA. ssherida@email.unc.edu
authors.forename: Stacey L
authors.initials: SL
authors.lastname: Sheridan
authors.forename: Michael
authors.initials: M
authors.lastname: Pignone
mesh_terms: D000328:Adult; D002983:Clinical Competence / Q000706:statistics & numerical data*; D003142:Communication; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D009657:North Carolina; D018570:Risk Assessment / Q000706:statistics & numerical data; D012577:Schools, Medical; D013337:Students, Medical / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires