Relative Risk (RR) is a measure used in epidemiology to determine the strength of association between exposure and disease. It is commonly used in cohort studies.
RR = (Incidence of disease in unexposed group) / (Incidence of disease in exposed group)
RR = [a/(a+b)] / [c/(c+d)]
where:
• a = Exposed individuals who develop the disease
• b = Exposed individuals who do not develop the disease
• c = Unexposed individuals who develop the disease
• d = Unexposed individuals who do not develop the disease
Interpretation of relative risk (RR):
• RR = 1 → No association (risk is the same in both groups)
• RR > 1 → Exposure increases the risk of disease (positive association)
• RR < 1 → Exposure is protective against disease (negative association)
Case control study |
Cohart study |
- Odds ratio |
- Relative risk - Attributable risk - Population risk ratio |