Relative effect
\[ Relative\ effect = \frac {Risk\ difference} {Risk\ in\ unexposed} = \frac {RD} {R_0} = \frac {R_1 - R_0} {R_0} = {RR} - 1 \]Risk ratio and incidence rate ratio (for small risks and short intervals only)
\[ Risk\ ratio = \frac {R_1} {R_0} \approx \frac {I_1 \times time} {I_0 \times time} = \frac {I_1} {I_0} \]Attributable fraction
\[ Attributable\ fraction = \frac {RD} {R_1} = \frac {R_1 - R_0} {R_1} = 1 - \frac {1} {RR} = \frac {RR -1 } {RR} \]Total attributable fractionn
\[ Total\ attributable\ fraction = \sum_{i = 1}^{n} {(AF_i \times P_i)} \]
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