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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

Semsem
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Awais
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1 Answers1

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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.

Eric Towers
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