COMBINING 2X2 TABLES THAT CONTAIN STRUCTURAL ZEROS

When one cell or more of a contingency table is necessarily zero, the table is said to contain structural zeros. These structural voids may be inherent to the problem at hand, or, in some applications, they may be introduced intentionally through the experimental design. With dat a classified by a third stratification variable, one needs a method fo r analysing a set of independent 2x2 tables. We propose Cochran-Mantel -Haenszel type analyses that combine observations across strata. We al so propose tests of hypotheses pertaining to the marginal and conditio nal probabilities.