Hello!
I am a Princeton Review instructor/trainer for the GMAT, so I hope I can help you out a bit.
The accuracy of our tests, in my experience, has been very good. You can expect a 30 point swing, in either direction, but an overall accurate picture of your capabilities. If anything, I have more often seen a few points lower on the actual exam, which is likely attributed to nerves and the like more than anything.
Now, that is not to say that our tests are currently identical matchings for the GMAT. At TPR we invest a lot of money in R&D, of which I have been a part, and we have found that the GMAT has recently been developing its scores in a different manner than our tests.
The difference basically comes down to two things. The actual GMAT allows for a few more missed questions on the Quant than do our tests, but maintains a harder level for longer. The actual GMAT also does throw more "insanely difficult" questions out on the Quant. (Keep in mind that the scoring algorithm has still been fairly accurate, despite the difference.)
The other difference is that the actual GMAT has been putting less emphasis on the location of the questions in calculating score for the Verbal section. The TPR tests have fairly similar question types, both in format and in difficulty, but we put a little more emphasis on the first ten questions. (Again, the accuracy on the Verbal, in my experience, is still very high.)
In short, your best bet is to base your difficulty expectations off of the GMATPrep software, downloadable from
www.mba.com . In my limited experience, the TPR tests are the most accurate predictors outside of the GMATPrep, with more students scoring LOWER on the actual GMAT than on the TPR exams by around 20-30 points. It is opposite for a lot other test prep companies.
Now, not all students have the same reactions to all tests, and I have had many students score 20 to 30 points higher as well. It is hard to predict, given nerves and additional prep time, etc, etc.
I hope this helps you! I know that I am biased, but I try my best to be objective.
Also, in case you are curious, TPR does offer a 15% discount on any course or tutoring if you purchase through the special offers on Beat the GMAT. Feel free to PM about anything.
Thanks!
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