Outline the problem of indices of therapeutic efficacy indices, 2: Description of the indices

The four indices for a binary outcome or therapeutic objective are: the odd s ratio, the relative risk, the absolute benefit and the number of patients to treat. For a continuous outcome, the effect size is the best choice. Th e odds ratio approximates the relative risk. The difference may be large in some instances. The number of patients to treat is the reciprocal of the a bsolute benefit. Although they are built on the same two quantities, they a re not interchangeable and should not be considered in the same way. Moreov er, their meaning is not straight-forward and they can be misused.