Cochran-Mantel-Haenszel Test

Mala Mahadevan explains the Cochran-Mantel-Haenszel test, with two parts up so far.  First, her data set:

Below is the script to create the table and dataset I used. This is just test data and not copied from anywhere.

Second, an introduction to the test itself and solutions in R and T-SQL:

This test is an extension of the Chi Square test I blogged of earlier. This is applied when we have to compare two groups over several levels and comparison may involve a third variable.
Let us consider a cohort study as an example – we have two medications A and B to treat asthma. We test them on a randomly selected batch of 200 people. Half of them receive drug A and half of them receive drug B. Some of them in either half develop asthma and some have it under control. The data set I have used can be found here. The summarized results are as below.

This series is not yet complete, so stay tuned.

Related Posts

Finding Gaps in Dates

Jason Brimhall shows how you can find gaps in your data: This method is the much maligned recursive CTE method. In my testing it runs consistently faster with a lower memory grant but does cause a bit more IO to be performed. Some trade-off to be considered there. Both queries are returning the desired data-set […]

Read More

Biases in Tree-Based Models

Nina Zumel looks at tree-based ensembling models like random forest and gradient boost and shows that they can be biased: In our previous article , we showed that generalized linear models are unbiased, or calibrated: they preserve the conditional expectations and rollups of the training data. A calibrated model is important in many applications, particularly when financial data […]

Read More


June 2017
« May Jul »