Table 4

Worked examples using the first study in table 3 (the Adventist study)

1The 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).
2Similar 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 0.2446372+0.3247362=0.165301. The 95% CI for the ln(RRR) is Embedded Image = (−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.