I am putting together a research proposal and would like to know if relative changes of a response variable should be handled differently when applying statistical hypothesis tests than of absolute changes.
As an example, say for instance you have 20 subjects and you randomly divide them up: 10 for placebo drug and 10 for drug X. The variable of interest could be the change in average heart rate before (average of 10 min.) and after (average of 10 min.) the drug is administered.
Would it make sense to normalize the changes by using % change of pre-drug (100%*(post-pre)/pre) as the test statistic or does this violate assumptions of most hypothesis tests?
Wondering if absolute changes should be used for comparisons instead of relative changes.