Instead of presenting a preset mixture of easy, medium, and hard questions the way traditional paper & pencil tests do, the GRE CAT selects questions for you based on your performance. It begins with a question of average difficulty. If you get that question right, the computer shows you a harder question next — if you get it wrong, the CAT gives you an easier question. So if you keep getting questions correct, the questions will increase in difficulty. If you slip and make some mistakes, the test will adjust and start giving you easier problems. The CAT literally adapts to your performance this way.

A CAT by definition provides everyone with a different mix of easy and hard questions. The very purpose of the adaptive format is to determine your score based on the level at which you answer questions correctly about 50 percent of the time. That means that the overall number you get right is not as important as the level at which you start getting about half the questions wrong.

On the CAT, you see only one question at a time, and once you answer a question it’s part of your score, for better or worse. You can’t go back to a question later on. That means you cannot skip around within a section and do questions in the order that you prefer. Instead, you have to do your best to get a question right the first time you see it.

GRE CAT questions are not all worth the same to your score. How much a question raises or lowers your score depends on when the question appears in a section. A question early on in a CAT section will affect your score more, for better or worse, than one later on. That’s because the computer makes larger scoring jumps in the beginning of a section to approximate your scoring level–it then makes smaller jumps as it fine-tunes your score. You can only get a high score if you answer enough medium problems correctly to see the hard problems.

GRE CAT Sections & Structure
The GRE CAT has three scored sections: Verbal, Quantitative (Math), and Analytical. The scored sections can be presented in any order, and have the following basic format:

Section Time Questions
Verbal 30 minutes 30 questions
Math 45 minutes 28 questions
Logic 60 minutes 35 questions

You can take as long as you like on any one question, but pace yourself to answer the all the questions in each section in the allotted time. Since there is a penalty for unanswered questions you should answer every question, even if you have to guess at random on the last few in order to finish the section on time.

The Experimental Section
In addition to these three scored sections, there may be one “experimental” section that looks just like one of the scored sections but does not count toward your score. ETS uses the experimental section to pre-test the questions that will show up on the scored sections of future GREs. The main thing for you to know about the experimental section is that it’s unscored.

This section looks just like one of the scored sections, so it’s important for you to do your best on it too — you won’t be able to tell which section is the experimental one anyway. A lot of people try hard to figure out which section is experimental. But all you will know is that if you have two sections of one measure type (and only one each of the others) then one of these sections is the experimental one.

Trying to figure out which section is experimental can actually be hazardous to your test score. There’s a good chance that you’ll guess wrong, and that’s not worth the risk. The effort you spend trying to guess which section is experimental can be a real distraction too. Finally, it’s doubtful that taking a snooze during a section will help you; it may actually lower your score if you can’t get your brain working again at full steam when the next section begins.

Sometimes there’s a fifth section called the “Research Section” which does not count toward your score either. The Research Section is optional, so there’s absolutely no reason for you to complete it.