1 | The female RR (and 95% CI) is 2.15 (1.33 to 3.47). Taking logs of all three numbers gives the ln(RR) and its 95% CI: 0.765468 (0.285179 to 1.244155). The two equations for SE give the results 0.244228 and 0.245045, which average out to 0.244637, our best estimate for the SE of the ln(RR). |

2 | Similar computations for men give corresponding results for the ln(RR) and SE of 0.746688 and 0.324736. The ln(RRR) is thus 0.765468−0.746688=0.01878, and its variance is 0.244637^{2}+0.324736^{2}=0.165301. The 95% CI for the ln(RRR) is = (−0.778101 to 0.815661). The estimated RRR and 95% CI are then the exponents of the ln(RRR) and its confidence limits, that is, 1.02 (0.46 to 2.26), to two decimal places. |

RR, relative risk; RRR, ratio of RRs.