Now suppose we have good reason to assume that "the two groups (treatment group and placebo group) have the same mean response at baseline". But one researcher considered the method with the assumption (Method 1) and another researcher considered the method without the assumption (Method 2). Both researchers got equivalent results.

Now my question is while the assumption of equal mean of baseline in different groups hold, then why do not considering the assumption make the method *LESS POWERFUL* while I am getting equivalent results from both the two methods?

The question arose after reading https://books.google.com.bd/books?i...ds of adjusting for baseline response&f=false

Thank you.