Relative Risk
Relative Risk
Incidence of the disease in the exposed / Incidence of the disease in the unexposed.
Odds Ratio
Rates Ratio
RR Value
IR = IRe/IRo
Risk Ratio
- CI and IR
Rate Ratio
CI = CIe/CIo = (a/(a+b)) / (c/(c+d))
IR = IRe/IRo
RR = 1: The disease and risk factor are unrelated
RR < 1: There’s a ‘negative association’ between the risk factor and the disease
RR > 1: There’s a strong association between disease and risk factor
IRe = Incidence Rate in Exposed
This can be used if we have IR instead of CI
IRo = Incidence Rate in Unexposed
"Those exposed to [exposure] have [RR] times the risk of developing [outcome], compared to the unexposed"
OR Value
OR = 1: No Difference
OR < 1: DECREASED Odds in Exposed
OR > 1: INCREASED Odds in Exposed
- No Incidence = No Risk
- Case-Control or Cross-Sectional
- We must estimate risk using odds
We need INCIDENCE (CI or IR)
Cohort or **
OR = (a/c) / (b/d) = ad/bc
"Those exposed to [exposure] had [OR] times the odds of developing [outcome], compared to the unexposed"