@hebegebe, right, but there would be correlation in that chart even if school/course difficulty is taken in to account.
As an example, say that a med school only has applicants from 2 schools, who send an equal number of applicants (and everyone gets the same MCAT score to simplify):
From School A, a GPA of 3.75-4 means a 90% acceptance rate and a GPA of 3.5-3.75 means a 50% acceptance rate.
From School B, a GPA of 3.75-4 means a 50% acceptance rate and a GPA of 3.5-3.75 means a 10% acceptance rate.
That chart would show a 70% acceptance rate for those with a GPA of 3.75-4 and 30% acceptance rate for those with a GPA of 3.5-3.75.