I just stumbled on this post, and just have a few things that I also looked in to on my own. The tests I ran had to do with the effect of missing questions early in the test. There is this myth floating around(still not dead) that the first few questions are more important than the rest. This is simply not true. As the GMAT writers say in the Official Guide, the first few questions are used to obtain an initial estimate of your ability, but that is pretty much what those questions do. From that point onward the student has to perform consistently to score high.
I ran these experiments on the Quant section:
Answer first 5 questions incorrectly and then answer the remaining 32 correctly.
Result: A final score of either Q49 or Q50(90 or 95%). I did 6 repeats. There is no way anyone can get a 99% with this performance, because this means you did miss some of the easier questions in the beginning, and those take a greater toll on your score than hard questions.
After missing the first 5 questions, the questions from 6 onwards were easy but the difficulty ramped up to the highest level by Question#12 or so. This means not all is lost in case you bomb the beginning of the test. This is important from a psychological point of view for the student.
At the end of the test the last five questions were easy, I call the last 7 questions of the GMAT the confirmation stage, this is where the algorithm is trying to confirm your score. Meaning if your last 7 questions are hard, then you did pretty well on the test. On actual GMAT my last 7 questions are almost always the hardest on the GMAT, and some of those I struggle to complete in 2 minutes, I tend to leave about 3 min per question for the last 7, if I can. Now in the tests I ran, the last 5 or 6 questions were easy, this is because the software needs to confirm if the first 5 questions I missed was by mistake or I really didn't know the concept.
The point of all this is that you just have to do your best in the beginning and even if you see a very difficult question in the beginning, it is okay if you let it go, in fact for many students this may be extremely important.
And finally a speculation on my part, the 9 experimental questions in the Quant are likely dispersed from Question#10 to 30, because I rarely see a random fluctuation on difficulty level of the questions on the GMAT in the beginning or the end of the test. However, I have seen extremely easy questions on the GMAT in the middle of the test, where they don't follow the difficulty pattern of the test. Let me repeat, this is purely a speculation on my part. Of course as a test writer I would disperse the questions randomly and throughout the test.
Enjoy,
Dabral
