Originally Posted by ElizabethN
the weirdness at the very top looks like a granularity effect to me - if you miss one question, you still get an 800, but if you miss two questions, you get a 780, not a 790. There are a relatively small number of versions of the test, each of which has a slightly different score distribution associated with it.

Agreed - you see the same effect in the talent search pool.

The College Board says you need to see scores 60 points apart to be sure that you're really seeing a difference in ability, and not just measurement error.