There is a really good
LizzyM "rungs on a ladder" analogy. Does anyone have that quote? It's one of the best that I've seen in correlating stats and "standings" on interview day. If nobody has it, I can paraphrase.
[EDIT] I found it! LizzyM's Staircase Analogy:
Your grades and scores (combined, if you will, with the formula GPA(10)+MCAT) along with your ECs, essays and LORs place you in one of many broad ranked categories. You can think of them as stairs on a wide staircase. (In other words, many of you can be on the same stair.) If a school selects you for interview, in all likelihood you are high enough on the stairs to be admitted or there is the potential that a good interview could boost you up enough to garner admission. That said, someone with a 4.0/40 and an amazing dossier of activities will start out on a higher stair and be more likely to be admitted if your interviews are about the same. Or, the other applicant could bomb the interview and move far down the staircase while you, with a great interview, move up. If a school looks at an applicant and says, "Even with a great interview, we couldn't possibly admit someone with an undergrad gpa of x.xx", then the school is doing you a disservice by inviting you to interview. If you get an interview, it should be a signal that you are "good enough" on paper and the next step is to determine if you are as good (or even better) in person.
In another post, she mentions that applicants generally don't move more than a couple 'steps' following an interview, barring something drastic (and usually bad). Essentially, strong applicants are playing to not lose, whereas weak gpa/mcat/EC applicants are playing to win.