Objective To assess whether the results of clinical trials on systematic reviews presented in different ways would influence postgraduates’ perception of risk and clinical decision after attending a research design course. Methods We distributed a questionnaire to all postgraduates who attended the final examination. The questionnaire presented the results of a systematic review. Data were presented in four different ways in the following order: as a relative risk reduction (RRR), as an absolute risk reduction (ARR), as the proportion of difference in event-free patients (EFP), and as the number of patients who needed to be treated to prevent one death (NNT). We asked all postgraduates to mark their decisions along a linear scale. Results We distributed and retrieved 342 questionnaires. Three were incomplete and excluded from our analyses. The results showed that the mean score and recommended level were significantly higher when data were expressed as NNT compared with RRR, ARR and EFP (Plt;0.01). There was no difference among RRR, ARR and EFP. However, 279 postgraduates’ score ranges were greater than 4 among the four different presentations. Conclusion The way of presenting data has significant influence on postgraduates’ perception of risk and their clinical decisions, even after a course teaching them about research design. Further improvements are needed for teachers on how to interprete different ways of presenting risk and their clinical importance.