The decision is based on all of the impacts
You are taking your decision based on the relative position of one impact, which does not mean anything, against another, which does not mean anything, against another, which does not mean anything, against another, which does not mean anything... and so on.
If the results obtained in such a way would be repeatable time after time I would change my mind but I have never seen anyone even trying.
Disclaimer: It would work for someone and his gun who shoots one-holers only, of course.
