[minhazm]

The pool is already pre-vetted through another company so in essence they are going to two sets of interviews. If you've already passed one set of interview then the probability that you pass the second one is much higher. That's how you can have a situation where a group of inexperienced candidates perform better than experienced interviewees.

[confidantlake]

Hit the nail on he head. You could do that with nearly any group. Coal miners, orphans, community college dropouts, deaf people, whatever. As long as your pool is large enough and you select the top handful out of that pool.