I am analysing data from a small study. There are two treatment groups and for each, one notes success and failures. For one of the groups, the number of successes is 0. I did an exact significance test, but reviewers of the paper want a confidence interval for the relative risk - in other words, a confidence interval for $p_1/p_2$, where $p_1=0$.
What should I do? The usual formula assumes that neither proportion is 0 or 1.