I am doing a project for share repurchase in the US. I am trying to estimate the operating performance before and after the repurchase announcement. And I am trying to adjust the performance to the industry level. The paper saying the results was estimated by the two tailed Wilcoxon test. Regarding this test, could I just test the unadjusted performance as a whole and then the adjusted performance as a whole? or do I have to put them as two different samples to compare? And how to use Stata to obtain such results? Do I have to find a code for that?
In Stata you can use
ranksum for that. As to the test, you can compare the performance before and after, which will give you two samples. You can report the results for both industry adjusted performance and unadjusted performance. But, adjusted performance makes more sense, since you are measuring the performance against your competitors.