Methods for binary, categorical and ordinal data

The Cochran-Mantel-Haenszel (CMH) tests are a collection of procedures that extend the simple chi-squared tests introduced in Chapter 4 to incorporate the multicentre setting. Landis, Heyman and Koch (1978) provide further details. 

For binary data in multi-centre trials we will have a series of 2 x 2 tables, one for each of the centres. For categorical and ordinal data with c categories, we will have a series of 2 x c tables. The CMH test in the first instance provides a single p-value for the main effect of treatment. 

---