GP is mistaken for sure.

But I think there's a difference between preparing for a specific test, and studying in general.

Let's say you have 2 days left to study for the GMAT. You could study the relevant math, reasoning or whatever. That might help.

But you'd do far better by working through problems in a Princeton Review GMAT book, and looking at their tips for the questions you got wrong.

The tips might be generic test-taking tips (e.g. eliminate obviously wrong answers) or they might be more specific (e.g. relating to specific types of problems found on the GMAT).