Straight from horse's mouth (or lets say Stanford GSB's Admission Blog) -
MYTH 1: The interview has a lot of weight so if I blow the interview, I have blown my chances of being admitted.
THE TRUTH: There is no specific weight assigned to the interview; the interview is one part of a comprehensive process. A positive interview does not guarantee admission, while a less than favorable interview does not, by itself, preclude admission. The written application, including the essays and letters of reference, is a critical part of the evaluation process. The interview is a key source of supplemental information.
MYTH 2: I received my interview invitation early in the round so it must mean I have a better chance of getting admitted.

