How are the questions calculated to a score?

[Michael]

Hello,

I just did the math of the GMATPrep again. I had 45 out 51, but only 24 of the 37 questions were correct. How does that work out?


Thanks,
Michael

[RonPurewal]

well, the test is adaptive. this means that if you're doing well on problems, you're going to earn the opportunity to attack harder problems. and if you're missing problems, then you're going to "earn" the opportunity to work on easier problems.

therefore, the problems will eventually regress to your ability level. this means that, unless you're either WAY up toward the top scores (780+) or WAY down toward the bottom scores (< 300), you should be getting comparable numbers of questions right and wrong after a while.
as an analogy, think about martial-arts tournaments in which you get to fight a better opponent after each win, but get demoted to easier opponents after each loss. in such a tournament, almost everyone is eventually going to wind up with comparable numbers of wins and losses, because they spend most of the tournament fighting opponents whose skill levels are roughly equal to their own. the only combatants who will have markedly different numbers of wins and losses are the very best and the very worst in the whole tournament pool.

or:

it's not the number of questions, it's the skill level of the questions.