At the moment, you're comparing apples and oranges. At best, you're comparing 2 different kinds of apples. On one hand, you have the official GMAT practice test software, which uses official (retired) GMAT questions and the official GMAT scoring algorithm. Also keep in mind that the test-makers have collected a lot of data on every single question, and every question has been asked in a formal testing environment, so that the well-prepared test-takers are trying their very best to answer every question.

While many test-prep companies have great practice tests, those companies would never suggest that their tests are as accurate as the official practice tests. The 3rd-party tests don't use retired GMAT questions, they don't use the official scoring algorithm, and the data collected on each question won't be as accurate, since those test-takers differ in many ways from those who take the official test.

So, while 3rd-party tests are great for practicing your test-taking skills, and for identifying weaknesses, you shouldn't use them as the sole basis for determining your present skills.

Cheers,
Brent

For all of the reasons I mentioned in my first post, the official GMATPrep test should be the most accurate of any practice test.

I should mention that you can take the GMATPrep tests multiple times. I mention this because when students see that the software contains two practice tests, they assume that they can take each test only once, and if they do take them a second time, the questions will be the same. This is not true. The GMAT is computer adaptive and questions are drawn from a large pool of questions. So, while you may see the occasional duplicate question, the majority of questions will be new to you.

If anyone is interested, I wrote an article for BTG on this topic: https://www.beatthegmat.com/mba/2010/03/ ... iple-times

Cheers,
Brent