Performing a Stratified NxP Test for Association

On occasion you need to perform a test for association between two categorical variables while stratifying, or controlling, for a third variable. The Cochran-Mantel-Haenszel test for association stratifies by a third variable to give proper weight to strata size. In the previous example, let s assume that you want to stratify your analysis by center to control for differences in center size. You can then run a Cochran-Mantel-Haenszel test like this  

The Cochran-Mantel-Haenszel (CMH) test contains three different tests for association. The following table describes each test and shows where the / -value can be found in your pvalue data set. 

Nonzero Correlation A significant p-value here indicates that there is a linear correlation between the two ordinal variables for at least one stratum. P CMHCOR 

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