GMAT Club Legend
Affiliations: HHonors Diamond, BGS Honor Society
Joined: 05 Apr 2006
Schools: Chicago (Booth) - Class of 2009
GMAT 1: 730 Q45 V45
WE: Business Development (Consumer Products)
, given: 7
Honestly I think its a function of two things:
1. Your consistency
2. Your overall score
First a primer on how adaptive tests work.
Each question has a difficulty assigned to it, and based on your estimated skill, a suspected target probability of your getting it correct. At the beginning of an exam, this may move signficantly as the system has little knowledge of your true ability, but even after just a few questions, it will begin to narrow in on your ability level. With each question, the system is trying to pick one that you have a 50% chance of getting right based on it's estimates. As you progress through the test, it narrows down this band.
The second thing you need to know is that the question set is finite, not just in the true sense, but also finite at a given level.
Lets pretend that raw scores indicate ability and imagine a bell curve of sorts. Logically speaking, the questions sets towards the middle will be more numerous, in order to ensure exhaustive sets for the vast majority of individuals, and also because the vast majority of people will end up bunched around the mean here - so it needs a larger set of questions just based on the fact that many people start the exam here, stay here, and never really move.
People on the opposite end of the spectrums are rare - how often do you hear about a 300 or an 800? The percentages speak for themselves. As such, the GMAT question sets are not evenly dispersed. That is, for every question that falls at an ability level, of say, "30", the GMAT doesn't create a corresponding question at the 50 level. They just don't have to - and it doesn't make sense to from a time/effort perspective.
Therefore, I think the repeat frequency is largely based on how consistent you are - that is, do you always score a "42" on every exam? If so, odds are, you'll be seeing a lot of "41" and "43" questions every time you take it. Thats part one. Part two is how high (or low) your score is. If you keep scoring 50 on quant, or 45 on verbal, there are far fewer questions it will pick from.
For me, for example, I'd say I saw at least a dozen or more repeat verbal questions (I scored 45), but on quant, I saw far fewer - in part because my score varied from 42-48, but also because, at these ranges, the question sets are larger.
So, to answer your question as to how many repeats you'll see? It' depends.