The downside of commercial GMAT materials

As a full-time GMAT tutor and a frequent reader of GMAT forums, I see many students who spend a decent chunk of their prep time using commercial materials. In a way, the use of commercial practice questions is almost inevitable: If you sign up with a company, you do so with the belief that its materials will accurately reflect what’s on the GMAT, and you approach the company’s materials accordingly. Unfortunately, there are two problems inherent in this situation:

#1: There is significant variation in the quality of practice questions out there, and if you’ve just begun prepping for the GMAT, it’s difficult to differentiate the good from the bad.

#2: Accurately replicating what appears on the GMAT Verbal is extremely difficult, if not downright impossible.

How do I know this? I used to help write these questions for one of the major test-prep companies. At this company , there was a fairly rigorous process for constructing Verbal questions, and, while I was there, I thought the team of writers did a decent job of creating these questions. The problem is that a decent job isn’t sufficient for accurately reflecting what you’ll see on test day.

Verbal questions on the GMAT (and all other standardized tests) are air-tight in their logic. Despite the somewhat pervasive belief that there’s an element of subjectivity in determining what is or isn’t correct on a Verbal questions, the test-makers conduct significant research to ensure that there’s a concrete reason that a wrong answer is wrong and a concrete reason that a correct answer is in fact correct. And, of course, they’re forced to do this; if they didn’t, they’d be liable to face a lawsuit from a disgruntled test-taker.

But, despite the best efforts of commercial companies, most of the practice Verbal questions have significant flaws—either because the question contains a loophole that the writers neglected or because it tests concepts in a way that the actual GMAT never would.

The problem here is not simply that you might do a few questions that aren’t test-like, but, rather, that you might develop incorrect habits toward the GMAT Verbal itself. Instead of working to understand the logic of the test-makers, you’ll be working to understand the fallible logic of the people at company X. For many people, there is already an element of ambiguity in GMAT Verbal, and the reality is that many of the practice Verbal questions from these large companies will only exacerbate this confusion.

So what should you do about it?

As a freelance tutor, I’m an unabashed proponent of all things “Official.” If you’re prepping for the GMAT, focus your Verbal efforts on official questions published by GMAC (the makers of the test). If you run out of these questions, move on to official LSAT questions.

If you’ve exhausted all these resources, then you might just have to turn to commercial materials. But do so with a skeptical eye.