I have a pre intervention group of $80$ patients and a post intervention group of $80$ patients. I need to know if there is a difference between the percentages of the pre group and post. example, after the intervention, there was an $80\%$ increase in asthma action plan use. Both groups differ, but are the same in number (if need be). Pre group is a chart review to see if asthma plans were done. Post group is the same measure, but patients maybe different.
Also, I need to know if after the intervention, did the number of visit change. example, the first group (pre group) had $80$ visits, the second group (post group) had 60 visits. Thanks
Generic process without knowing more about your experimental design:
Step 1) Perform an F-test on the two groups to determine whether the variance in the two groups is justifiably the same. If so:
Step 2) Perform a t-test on the two groups to determine whether the observed difference in mean is justifiably different from "nothing".
If the variances are not indistinguishable, use the different-variances version of a t-test. The power of the test is reduced and the computation is harder, but you should be using software so this latter problem will (should?) not be significant.