I'm wondering how odds ratio is computed. I thought that it is (n11/n12)/(n21/n22), but it is not what fisher.test() computes. Could somebody let me know?
> n11=3 > n12=1 > n21=1 > n22=3 > > n1_=n11+n12 > n2_=n21+n22 > > n_1=n11+n21 > n_2=n12+n22 > > x=rbind(c(n11,n12),c(n21,n22)) > > threshold=dhyper(n11,n1_,n2_,n_1) > probability=dhyper(0:n_1,n1_,n2_,n_1) > sum(probability[probability<=threshold]) [1] 0.4857143 > (n11/n12)/(n21/n22) [1] 9 > fisher.test(x) Fisher's Exact Test for Count Data data: x p-value = 0.4857 alternative hypothesis: true odds ratio is not equal to 1 95 percent confidence interval: 0.2117329 621.9337505 sample estimates: odds ratio 6.408309 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.