i would guess that 10% get interviews. and 6% get in. thats a little over half of the interviewees, because some will decide to go somewhere else.
when i say 10% that does not mean that you will get an interview for every 10 schools you apply to, most schools are after the same people. and if you are a non resident applying to a state school your odds are probably closer to 1 or 2% of getting an interview