In this chapter, we continue our study of models for several 2× 2 tables. After a brief comment on two other types of models, we return to the logit models with a focus on checking their assumptions and extending their scope to designs other than the prospective product binomials design. The specific aims in these pages are for a series of 2× 2 contingency tables:

• To introduce the stratified risk difference and risk ratio models. • To derive the exact distributions of the stratum additive statistics used for testing the as-

sumption of a common odds ratio, and of a linear trend on the log-odds scale.