Mantel-Haenszel X2 test

Test for a null hypothesis of no overall relationship in a
series of 2x2 tables for stratified data derived either from a cohort or a case-control study. It allows analysis of confounding and gives an adjusted odds ratio or relative risk. It can be used on categorical or categorized continuous data. The test is only valid when the variance of observed data is . It is inappropriate when the association changes dramatically across strata. It is, however, applicable for sparse data sets for which asymptotic theory does not hold for . The test statistics, , has approximately a Chi-squared distribution with df = 1. Sometimes also called Cochran-Mantel-Haenszel test.