vague question..but still an interesting one. a lot of people have told me that most interviews are just to see if you can converse properly in english and put forth a solid personality with good social skills. i guess the only way you can really screw up an interview is because of a language barrier or being caught lying about something. i have never done one yet though..so what do i know??
I have been to five interviews so far and I asked that question to all of them. I didn't get straight forward answer from Columbia and CRW. However, USC told me it is counted 1/3 in the acceptance process, and temple said it is counted 10% in it. It is different from each school. I heard that if you get interviews from UOP and Tufts, you are (garanteed) in. I hope this helps. Good luck!
I think the interview counts more than most schools let on. Think about it.
They have a stack of really qualified applicants and how are they going to choose between them all when they all statistically deserve a shot. The interview is the only real way to get a sense of the differences. People are more than pieces of paper and stats.
I believe it counts 1/3 at UNC. I do know that as students we get to interview applicants and then have to fill out a lengthy form with ratings and written feedback. This one student interview (3 total, 2 faculty and 1 student) can be enough to prevent someone from getting in. As an example, someone I interviewed last year told me he was applying to school because "my girlfriend and mom keep nagging me to so I thought I guess I should". Needless to say, I didn't have the best things to say about him!