why you shouldn't worry (too much) about percentile rankings

I’ve already met some brilliant MBA candidates in my first few weeks here in New York, but the most gifted GMAT student I ever tutored was probably a young woman I met in DC, before my Manhattan days.  She was a cum laude graduate of Duke University’s economics program, and she had already earned a ridiculously high score on the GRE.  She was solidly scoring in the 700s on her GMAT practice tests, and just wanted help getting her math score “as close to perfect as possible.” I’ll be honest:  there’s a pretty good chance that this particular GMAT student (let’s call her Susan) was smarter than I am, and that’s a beautiful and intimidating situation to be in as a GMAT tutor.  I suspected (correctly) from the start that she didn’t have any fundamental GMAT math weaknesses; all I could offer was some practice questions designed to help her make connections on the hardest GMAT math questions.  (Basically, math formulas are of limited value on hard GMAT questions, and you need to be able to "see" a connection before you'll have any prayer of getting the right answer.  I'll expand on this in a future blog post.)

Basically, tutoring Susan meant spending two hours inventing the hardest GMAT-style questions I could possibly come up with.  I loved it, and I probably learned more from the experience than she did.  Occasionally, I’d manage to stump her, and that was great.  After about eight or ten GMAT tutoring sessions, we decided that she had probably “worked her GMAT math muscles” as much as was reasonable, and she went to take the test.

And she was bitterly disappointed when she looked at her percentile ranking on the GMAT.  She scored in the 99th percentile on the verbal, and her composite score was also in the 99th percentile.  Her quantitative score, however, was only in the 84th percentile.  How could this be true?  She scored a 760 on the GMAT, but somehow wasn't even in the top 10% in math? WTF?

If you have any experience with the GMAT, you surely realize that a score of 48 on the quant section is pretty darned impressive.  (Frankly, anything above a 45 should, in theory, be good enough to allay any legitimate fears that an MBA admissions committee might have about your quant skills, but that's another topic entirely.)  For whatever reason, however, there are lots of impressive math whizzes taking the GMAT.  A full 20% of GMAT test-takers earn a score between 47 and 51.  The score distribution, then, is not a bell curve at all for the quantitative section--it basically looks like a slowly increasing function, with an extra little jump at the end.

I admiringly call this the "Asian effect."  Based on anecdotal evidence, I'm convinced that most of the people who achieve quantitative scores in this range are not products of the United States education system.  (News flash:  by global standards, we Americans are generally pretty lousy at math.)  Basically, there are a ton of people in Asia who demolish the quantitative section of the GMAT, and they make a whole lot of GMAT-takers feel inadequate when they see their percentile score.

Interestingly, the GMAT verbal score distribution is almost a perfect bell curve.  Similarly, the GMAT composite score distribution is also a fairly non-skewed bell curve.  This suggests that most of the GMAT "quant ninjas" are not particularly great at verbal.

The bottom line?  If you're trying to get into top MBA programs, it's probably OK to have a math score "only" in, say, the 70th or 75th percentile.  Don't let the percentile score mess with you:  if your raw GMAT quant score is well into the 40s, it probably won't, by itself, sabotage your MBA dreams.