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SigmaCalc
A direct comparison of event probability between two groups — the standard measure in cohort and clinical trial studies.
Unlike odds ratio, relative risk requires knowing the true incidence in each group — which means it's appropriate for cohort studies and clinical trials, but generally not for case-control studies where the sampling itself is based on outcome status.
A relative risk of 1 means equal risk between groups. A relative risk of 2 means the exposed group is twice as likely to experience the event; 0.5 means half as likely — it's a direct, intuitive ratio of probabilities.
Relative risk
3
RR = [a÷(a+b)] ÷ [c÷(c+d)]
What you entered
Risk of the event in the exposed group
30 ÷ (30 + 70)= 0.3Risk of the event in the unexposed group
10 ÷ (10 + 90)= 0.1Relative risk
0.3 ÷ 0.1= 3Result
Relative risk: 3
A relative risk of 3 means the exposed group is 3× more likely to experience the event than the unexposed group.