I've been wondering whether there are some clues that your interviews will be more likely to result in acceptances. For instance, if it's a clue that you're invited early to interview at a school with rolling admissions, and whether you get many early invitations or not. And, as you said, whether you have a high II/apply ratio.
Anyway, I agree that, although acceptance from the II pool is a 35% average across schools, very roughly, one's individual chances vary widely based on background and interviewing skill. But let's assume 35% for fun!
Then:
http://www.wolframalpha.com/share/clip?f=d41d8cd98f00b204e9800998ecf8427evpilk3saf3
Edit: Graph shows chance of full rejection on Y, # of II attended on X