Estimation of the common risk difference in stratified paired binary data with homogeneous stratum effect.

McNemar's test is commonly used to test for the risk difference between two binary variables on matched pairs. For stratified paired binary data, recently a test for the homogeneous stratum effect (HSE) has been developed. If HSE is rejected, then McNemar's test should be applied by stratum; otherwise, in this article we propose a concept of common risk difference (CRD) across the strata and derive point estimators and confidence intervals for CRD. We use a cancer study for illustration and conduct simulations to recommend point estimators and associated confidence intervals with good statistical properties.