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What is a Computer Adaptive Test and why should I care?

  • by John
  • Jun 10, 2011
  • GRE Blog

The GRE is a Computer Adaptive Test, which means that the test constantly adapts to your ability level, giving you harder questions if you answer questions correctly and easier ones if you get them wrong. Why would anyone design such a test? And how should it affect your test-taking strategy?

Why the GRE is Adaptive: An Allegory

Suppose you decided to test the mathematical abilities of a bunch of 8-year-olds by giving them all a calculus test. What would happen? They would all fail, and probably one or two of them would start crying, and their parents would complain. But most importantly, they would all get the same score– zero– so you’d have no clue which of them were good at math. You’d have the same problem if you gave a bunch of physics PhDs an arithmetic test: they’d all get perfect scores, and you wouldn’t be able to tell which of them were better than others.

How does this relate to the GRE? Well, the GRE is trying to test the abilities of a group with a wide range of abilities, from math majors who know everything about math but speak in monosyllables to English majors who know all about dactyls but can’t calculate a tip without an iPhone app. If the GRE were a paper-and-pencil test, this would be a problem: if they made the math section really hard, all the humanities people would get a zero and you couldn’t tell the difference between them, but if they made it really easy, all the math people would get a perfect score and they’d all look the same.

Hence the adaptation! Basically, the GRE constantly adjusts in order to get a good measure of your mathematical ability: if it figures out early on that you kind of suck at math, it will give you easy questions to try to figure out whether you really such or just kind of suck. If you’re really good at English, it will give you tougher and tougher questions to figure out whether you’re the next poet laureate or just pretty well-read. Basically, the whole thing is pretty clever.

How does this affect my test-taking strategy?

Glad you asked! In three ways:

  1. You can’t go back. Since your answer to the last question affects what the next question will be, you have to answer every question in order– no saving the tough ones for the end or avoiding topics you don’t know much about, the way you might have on the SAT. Since you’re going to have to answer every question anyway, you should learn to eliminate ridiculous answers even if you can’t figure out the right one: Just because you’re guessing doesn’t mean you have to guess randomly.
  2. You can game the system a little bit by spending a bit more time on earlier questions. Broadly speaking, the test will determine your approximate score from the earlier questions, then refine its estimate on the later questions. If you answer the first ten questions right, the computer thinks to itself that it probably has a 700-level test-taker on its hands and starts trying to figure out whether you’re a 720 or a 780. This is great for you, since even if you can’t get a few of the later questions you might still end up with a 720.
  3. You can’t really game the system all that much, so don’t bother trying. The GRE wasn’t designed by idiots: If you answer the first ten questions correctly but then fail the rest of the test, you’ll get bumped back down to a lower scoring bracket. So don’t go spending all your time on the first questions and none on the rest. A good rule of thumb: You have a little more than 1 minute and 30 seconds per question; spending 2 minutes each on the first ten questions and correspondingly less on the later ones isn’t a bad idea.
  4. Don’t Try to Guess What the Computer is Thinking. Many students think they can figure out whether they’re doing well or poorly from the questions they’re getting: If the question they’re on is easier, they figure they must have answered the last question wrong. This is (1) inaccurate and (2) useless, so stop thinking about it. It’s inaccurate because you can’t really tell which questions the computer thinks are “hard,” and there’s a bit of random chance in which questions you get anyway; it’s useless because thinking about anything besides the question you’re on is pretty much futile. Don’t psych yourself out.

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Photo credit Charlie Evatt under a Creative Commons license.

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