Confidence intervals of risk ratio library(epitools) tabrisk=matrix(c(800,17,3,1),nc=2) riskratio(tabrisk, method='wald') riskratio(tabrisk, method='small')

Gives something like this (results edited for clarity): riskratio(tabrisk, method='wald') $data Outcome Predictor Disease1 Disease2 Total Exposed1 800 3 803 Exposed2 17 1 18 Total 817 4 821 $measure risk ratio with 95% C.I. Predictor estimate lower upper Exposed1 1.00000 NA NA Exposed2 14.87037 1.624062 136.1573 $p.value two-sided Predictor midp.exact fisher.exact chi.square Exposed1 NA NA NA Exposed2 0.08766274 0.0850061 0.001792525 > riskratio(tabrisk, method='small') $data Outcome Predictor Disease1 Disease2 Total Exposed1 800 3 803 Exposed2 17 1 18 Total 817 4 821 $measure risk ratio with 95% C.I. Predictor estimate lower upper Exposed1 1.00000 NA NA Exposed2 11.16667 1.219563 102.2452 $p.value two-sided Predictor midp.exact fisher.exact chi.square Exposed1 NA NA NA Exposed2 0.08766274 0.0850061 0.001792525