<p>I would say that the true probability of getting into RSI is negatively correlated to your estimated probability of getting in. Almost any RSI alumnus (including some of the most accomplished) will tell you that he/she had no idea why he/she was selected. </p>
<p>There is certainly no single factor that will get you in or not get you in to RSI. There are people who get into RSI w/out taking the PSAT, and there are even more people who get rejected w/ perfect test scores. I would echo LuoSciOly… they can somehow tell who is genuinely in love w/ science and who will be able to handle the absolutely insane workload.</p>