Choose statistical test method: comparing the frequency of a disease (only interested the disease post-procedure) in 2 groups of patients I am working on 2 groups of patients, group A and group B. The patients in both groups have received a same procedure. We have observed the patients before and after the procedure.
Suppose there is a disease (Ds), some of the patients have this disease before the procedure, some of them have developed this disease after the procedure, and others don't have this disease during the observation.
I want to do a statistical test to see if the post-procedure disease frequency in group A and group B are different.
What will be the best statistical test to process? Which set of data shall I work with? (# of patients with Ds post-procedure/# of patients without Ds) or (# of patients with Ds post-procedure/# Total patients in each group)




Group
# of patients with Ds post-procedure
# of patients without Ds
# Total patients in each group




Group A
179
485
1398


Group B
801
3933
8362




*the patients with Ds pre-procedure are not listed in the table since we are only interest the patients with Ds post-procedure.

You do not need to use the total number of patients. In order to compare both groups, you only need to take into account the number of patients without the disease before and after. Then it becomes a very common statistical analysis performed via t-test
