Say that in order to determine what
B is, you analyze
A. But then someone analyzes
B in order to determine what
A is. In my language, we would say that this procedure "begins in the wrong end". What is an appropriate English idiom or phrase here? The only one I can think of now is to say that the procedure has been "turned on its head".
EDIT: I intend to use the appropriate phrase or idiom in a scholarly paper, so it needs to be polite enough for that context.