William,
So the way the CATs I've taken usually work is they start out with the hardest of questions in each of the test categories to see where your strengths/weaknesses are. Regardless if you answer these questions correctly or wrong, the questions will move on.
In the next phase, the CATs will go back and look at the first round for questions that you got wrong and then hit you with round 2 of the hardest questions to make sure that wasn't a fluke that you got it wrong. If you get round 2 wrong, it will step back the level of difficulty (and the max score) of the question until it figures out what your minimum proficiency level is.
In the third phase, if you begin getting questions right, it will ramp up the difficulty and score of that section until you get a string of questions right enough to satisfy the system that that "level" is your maximum level of proficiency in that section. It will then move on to the next section and repeat Phase 2.
In Phase 4, it will hit the sections you got right to make sure those weren't an anomaly. If you get a second/third round of the hardest questions right, it'll basically give you that score level for those sections. If you start getting those wrong (and especially if you were flustered from failures in the previous section), it will begin dropping your average "level" and corresponding score in those sections you initially got right, circling you back into Phase 2 for those topics you're normally strong in. Getting flustered like this could completely kill your score even in a section where you previously answered the hardest question on the test correctly.
My memory is that you have to pass at least two Domains with a very high score, even if the overall test is a 70%. So if you didn't get that in at least two Domains, I could see the system going back and trying to get you to pass the hardest questions over and over again. You would effectively never leave Phase 1 until you got questions from at least two domains at the hardest levels right. Even if you got them right by accident, they would go back and hit you in Phase 3 and find out it was luck, dumping you back to Phase 1 again.
This does not necessarily represent the CAT for the CISSP. It is merely a reflection of my observations and experiences taking CATs in other exams. I never sat for the CISSP CAT exam.
Sincerely,
Eric B.
