difficulty of the practice exams

[xxchen]

just a few observations
I feel like the first few practice exams are much more difficult than the latter ones and the real gmat (in regards to math).
I can't finish the math section on the first three exams on time, but had no problem with the latter three.
Also, I noticed 80% of the questions I got from the first few exams were all in difficulty range of 700-800...but in the latter three 95% of the questions are 600-700...I think the question bank might be out of questions?
I also noticed that the real GMAT questions tend to be shorter, while manhattan gmat's questions are longer and more convoluted (making it not necessarily more difficult, just require longer time to read and understand the question)

[RonPurewal]

I feel like the first few practice exams are much more difficult than the latter ones and the real gmat (in regards to math).

the six practice exams are actually pulled from a common pool of questions, so this can't be the case. in fact, if you reset the practice tests after you've taken all six, you'll notice, in the earlier tests, at least some questions that showed up in the later tests the last time around.
what i'm saying here is that "the first three tests" and "the last three tests" aren't distinct; the questions are all pulled from the same source

the EXCEPTION here arises if you are a VERY high-scoring student. as of right now, there aren't enough 700+ questions in the pool to accommodate all six tests for a student who regularly scores in the mid-700's and higher.
if this describes you, then you'll probably notice a glut of 600-700 questions later on in the tests. that's the point at which you simply exhausted the supply of difficult problems!

I can't finish the math section on the first three exams on time, but had no problem with the latter three.
Also, I noticed 80% of the questions I got from the first few exams were all in difficulty range of 700-800...but in the latter three 95% of the questions are 600-700...I think the question bank might be out of questions?

yes. read explanation above.

we are currently working at a feverish pace on making more difficult questions for the cat tests. stay tuned.

I also noticed that the real GMAT questions tend to be shorter, while manhattan gmat's questions are longer and more convoluted (making it not necessarily more difficult, just require longer time to read and understand the question)

this is a problem that we are addressing in writing the next generation of cat problems (as we speak).

the flipside of this problem - which is a good thing - is that the "longer", "more convoluted" problems will force students to practice better TIME MANAGEMENT. since most students dwell on problems for too long, that's a nice positive externality.
but, yes, the next generation of problems will be lighter on the manual labor.

incidentally, the real exam also has a fairly large number of experimental questions (about 8-10 per math section), which are of random difficulty levels. since you're clearly a high scorer, "random difficulty levels" will be, on average, significantly easier than your standard difficulty level, so that factor will also work in your favor on the exam.
our exams don't currently have experimental questions, although that's a feature that we'll eventually build in.