Several weeks ago, GMAC (the people who make the test) held its biennial Test Prep Summit, and we’ve all been writing articles about it ever since. I have more for you today “ and enough for several more articles after that, including another idioms article that I had hoped to have for you today, but the research isn’t done yet. Instead, today I’m going to share with you some very useful knowledge that has been published by Lawrence M. Rudner, Chief Psychometrician of GMAC, in his Demystifying the GMAT article series.
The below quotes are all from Dr. Rudner and all quotes are copyright 2011 Graduate Management Admissions Council. The headers below are the names of the individual articles from which the information and quotes came.
Demystifying the GMAT: What Is on the GMAT?
First of all, at heart, the GMAT is a reasoning test, not a memorization test. There are many facts and rules that we need to know in order to succeed on the exam, but those facts and rules are just the beginning.
We make the GMAT exam rigorous primarily by including test questions that tap the higher order thinking skills of analysis, synthesis, and evaluation.
And the higher you want to go on the exam, the better you’re going to have to be with those higher order skills “ one of the major ways in which the test writers make harder questions is to make us do more sophisticated reasoning to get to the answer. The actual facts and rules will only take us so far.
Demystifying the GMAT: Scale Scores
First of all, what does scale scores mean? There are three different scoring scales on the GMAT. The individual Quant and Verbal sections are scored on a scale of 11 (low) to 51 (high), and then those two scores are combined (via a proprietary algorithm) to arrive at a total score of 200 to 800. (This is the score everyone talks about when they say, What did you get on the GMAT?) Finally, the AWA (essay) section is scored on a scale of 0 to 6. Further, each score on each scoring scale is associated with a certain percentile ranking. For example, a 45 on the Verbal scale is the 99th percentile, and a 700 on the Total scale is the 90th percentile.
So what do these numbers means? And how do they change over time? The scaled scores don’t actually change:
A Quant score of 43 in 2002 represents the exact same level of ability as a Quant score of 43 does in 2011.
The percentiles, though, are more narrow in scope:
Percentiles report ability relative to test takers from the past three years, calculated from a rolling average, and thus can change over time.”
As the pool of test takers changes over time, the percentile rankings associated with specific scaled scores can change. If more highly-educated people start to take the exam, for example, that shifts the relative rankings of the entire pool “ and that is exactly what has been happening over the last 5 to 10 years. The GMAT’s worldwide expansion has allowed a greater pool of highly-educated testers to access the test, so the quality of the entire testing pool has been shifting upwards.
That’s kind of esoteric “ let’s look at a real example. Last month, when GMAC released the new scaled score to percentile rankings chart, the top Quant scaled score of 51 was reduced to the 98th percentile (previously it had been the 99th). What does that mean? You still have to know and be able to do the same kinds of things to get a 51 as someone did 10 years ago “ that is, the necessary skill level hasn’t changed. But 10 years ago, only 1% of the test-taking population could also do those things as well as you could. Today, 2% of the test-taking population can perform at that level.
Demystifying the GMAT: Reliability
Did you know this?
Every GMAT test taker will see the same number of each type of question. For the Quantitative section, the mix of data sufficiency, problem solving, algebra, geometry, arithmetic function, applied and formula-based questions will always be the same.
That doesn’t directly help us to study “ we still have to study everything “ but it does reassure us that the GMAT is a fair test. If we’re going to spend all this time and energy studying this test, it’s nice to know that this test is fair (unlike some of the other CAT-based exams out there.) There are other factors that influence the fairness of a test, of course, but consistency across testers is a big one. (Fairness is also the main reason, by the way, that GMAC has eliminated American-centric language and other forms of bias.)
I often speak with students who worry that there are different question pools in different countries; for example, people sometimes wonder whether China and India have harder pools of quant questions because students in those countries tend to be very good at quant “ and so, if you’re not as good at quant, then you’ll be at a disadvantage if you take the test in those countries. That’s not the case and you don’t need to worry about that. You are being tested fairly across the entire pool of GMAT test takers.
And I’ll let Larry finish with this comment:
No test is perfectly reliable. Some small random variation of scores is always expected. As such, we encourage schools to take the standard error of measurement into account when reviewing scores. Candidates whose scores are within 30 points of each other should be treated equally.
(1) We do, of course, need to study the content that is tested on the GMAT, but if we want to really maximize our scores, then we have to get better at process, reasoning, thinking, analyzing “ these are really the skills that are tested (especially at the highest levels) on the GMAT.
(2) The score scales do map to different percentiles over time as the population of test takers changes, but that’s true for everyone taking the test and, as such, doesn’t affect our chances for admission. So don’t worry about it!
(3) The GMAT is one of the best exams available as far as fairness and reliability are concerned, but every test in existence has a standard measurement of error. There truly isn’t a statistically significant difference between, say, a 700 and a 720. Obviously, we would all prefer to have the higher number, but in this case, the difference is just psychological.