Less than 1 hour. Got into all 6 interviews I chose to attend.
Did not have amazing numbers and was not a URM, so I guess I just interview well.
Seriously...be yourself. Don't over think. I did nothing but be myself...I had lunch with a doctor before I applied and learned some stuff about reform etc. that was my only true preparation.
Meanwhile my friend prepped for hours and hours and got denied from tons of places cause he tried to "script" his interview.
Believe in yourself...I'm sure you have a good personality dude