# Comparison of proportions using McNemar's Chi-Square using Pre- and Post- data for two disease conditions

This question follows-up on the post: What is the difference between McNemar's test and the chi-squared test, and how do you know when to use each?

I am examining a pre- and post- intervention data on two disease conditions. The above post described the use of McNemar's test for 1 disease before and after an intervention was administered to a sample.

I have two contingency tables, which look like:

            **Disease A**

After
|no  |yes|
Before|No  |41  |11 |
|Yes |32  |39 |

**Disease B**

After
|no  |yes|
Before|No  |41  |11 |
|Yes |32  |39 |


Question: I would like to compare the proportions of:

(1) Those that went from "Yes" to "No" pre to post for Disease A vs. Disease B

(2) Those that are "Yes" after treatment ("After Yes"/"Total N") vs. those that are "No" after treatment for Disease A vs. Disease B.

How do I compare the two proportions in the above two questions ?

Again, the data is drawn from the same sample and anyone with Disease A could also be positive for Disease B at the same time. The same intervention is used to treat both A and B.

• What question are you trying to answer by doing that? – Björn Feb 4 '19 at 5:54
• For Q(1), I'd like to know whether the rates of remission (going from yes to no post intervention) are significantly different for disease A and disease B. In other words, if disease A shows 40% remission and disease B shows 60% remission, are these rates significantly different? – user81715 Feb 5 '19 at 16:42
• What is that trying to answer? Whether the intervention is more effective in one disease or another? – Björn Feb 5 '19 at 17:36
• exactly. whether one of the two diseases responds less well to intervention when compared to the other. – user81715 Feb 5 '19 at 20:35