One of the most commonly misunderstood aspects of the computerized GMAT exam is its adaptive questioning and scoring system, known as CAT. Short for Computerized Adaptive Testing, CAT is a system designed to continually assess the test-taker’s aptitude and adjust the difficulty of the questions on the exam. A correct answer will yield a question deemed more difficult, while an omitted or incorrect answer will result in an easier next question. Put simply, the better you are doing on the exam, the harder it gets. Start to flounder a bit and the exam will take mercy, easing up on the harder stuff. Ultimately, a final score will be determined by two factors: number of correct answers and difficulty of those questions.
The exam begins by assuming you are of average aptitude, giving a first question of medium difficulty. If you get the first question correct, your second question will be more difficult, and, as a result, more valuable to your final score. Conversely, missing the first question will make the second question easier and thus less valuable. This varying difficulty and value creates a problematic scenario: early questions are more important than later questions. Omitting or incorrectly answering an early question will create a “score gap” that cannot be made up. In other words, messing up early on can cause a level of damage to your score that later questions are unable to salvage.
Imagine a ten question exam taken by three students, A, B, and C, with each question rated in difficulty from 1 to 5. Each question is worth the same number of points as the question’s difficulty level. A correct answer will increase the difficulty of the next question by one level to a maximum of 5, while an incorrect answer will decrease the difficulty level to a minimum of 1. Question 1 is always of level 3 difficulty. This means the maximum number of points that could be received is 47 (3 + 4 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 47).
Student A misses question 1, missing out on those three points, then answers all of the remaining questions correctly. Question 2 is now a level 2 problem, worth two points. Despite the relatively minor value of question 1, Student A will receive a score of only 39 points (0 + 2 + 3 + 4 + 5 + 5 + 5 + 5 + 5 + 5 = 39). Missing a three-point question at the beginning of the exam resulted in a total loss of eight points! We begin to see the value of the first questions in this scenario.
Student B misses question 5 after getting the first four questions correct, then answers all of the remaining questions correctly. Student B will lose five points from question 5, but will actually end up with a higher score than student A: 41 points (3 + 4 + 5 + 5 + 0 + 4 + 5 + 5 + 5 + 5 = 41).
Student C answers every question correctly except for question 10. From what we have seen to this point, it should not be surprising that student C will receive the highest score of all, 42 points (3 + 4 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 42).
Despite each student answering the same number of questions correctly, the percentage of possible points received by each student is 83%, 87%, and 89%, respectively. While this scenario is not exactly how the GMAT works, it provides a simple example of how an early mistake can keep you mired in lower difficulty (and lower value) problems for a longer period of time. With this knowledge in hand, remind yourself to take the requisite time on your first few questions and speed up as you progress.
One other aspect of the CAT system that many do not consider is the inability to go back to previous questions. Since each question after the first is determined by your previous level of success, the GMAT will not allow you to return to an already-completed question to change your answer. This reemphasizes the need to spend as much time as you need on your first questions, but should also clearly highlight the fact that omitting any answer on this exam would be exceptionally foolish. Further, there are stiff penalties for leaving questions unanswered, so be sure that you always answer every question. Even if you have to guess on your last few questions, take solace in the fact that these questions are less valuable and an incorrect answer is always better than no answer at all.
Now that you know how the GMAT works, you’ve taken your first step to formulating a solid test-day strategy. Try to avoid being wrong, and if you have to be wrong, make sure you save it for the end!