Interpreting Results from Randomized Trials .

Clinicians regularly encounter effect measures such as RR, OR, HR, RD, ARR, RRR, and NNT when interpreting dichotomous outcomes in trials and observational studies. Understanding what each means—and how they differ—is essential for translating evidence into practice. Relative measures (RR, OR, HR, RRR) describe proportional differences between groups, while absolute measures (RD, ARR, NNT) ground results in the actual change in event rates. RR compares risks directly; NNT expresses how many patients must be treated for one additional benefit; RRR reframes RR as a percentage difference; HR incorporates time-to-event information; and OR approximates RR only when events are rare. Across all measures, interpretation hinges on the 95% CI to judge both the magnitude and certainty of effect.