Multiple comparisons and association selection in general epidemiology.

In this issue of the journal, Prof. Jon Wakefield provides a contribution to the complex topic of screening genetic associations. My comments here are intended to clarify some points and outline connections of his discussion to broader problems, describing how methods such as Wakefield’s can be appropriate in epidemiology beyond genetic research. I will also comment on a few aspects of his presentation related to technical issues. I will assume (as does Wakefield) that the reader is familiar with the terminology of Bayesian statistics as well that of conventional (frequentist) statistics. I will start with a comment on interpretation of P-values, and then turn to the issue of multiple comparisons.