In this post I would like to expound upon a theory of mine that gets at the slight differences in the scoring algorithm on the Quant and Verbal sections of the GMAT. In a previous post I commented on the fact that although on the Quant section the number of questions you get right has very little to do with the score you receive, on the Verbal section the number of questions right matters much more. I don’t think there is any official explanation for this phenomenon, but I have long had a theory that I think makes pretty good logical sense. Understanding the nuances of the algorithm can help you learn what exactly you need to do to achieve a high score on each section.
Quantitative questions, by nature, are completely unambiguous. If x equals 10, then x can’t also equal 15 (well ok it can in a quadratic equation and in some other special situations, but you get the point). Verbal questions, on the other hand, are by nature a little less black and white than Math questions. Of course GMAC writes questions that are technically unambiguous, but the problem is that it is tough to make a Verbal question really, really hard without crossing the line a little into ambiguity, so there tends to be a limit to how hard a Verbal question can realistically get. That problem does not exist on Quant. There is almost no limit to how hard the test writers can make a Math question and it will still be completely unambiguous, completely black and white.
This helps explain the differences in the algorithm on each section. On Quant, the questions can pretty much just keep getting harder and harder until nearly everyone would get the questions wrong. Really only at the very top reaches of the Quant section scoring spectrum will people get fewer than about 1/3 of the questions wrong. So for most people the differentiating factor in scores on the Quant section is just the level of difficulty of the questions that test takers are able to get right consistently. If your breaking point is 650, your score is 650. If your breaking point is 720, then your score is 720. The number of questions that you get wrong is not really a factor except, perhaps, in differentiating between people at the tippy top of the scoring spectrum.
But since there is more of a limit to how hard a Verbal question can get (again before it starts to drift over the line into “ambiguous/unfair question territory”), the number of questions right and wrong starts to become more of a differentiating factor. That’s because many test takers get up into the very hardest Verbal questions so at that point the main way for the algorithm to differentiate between top scores is just by number of questions wrong. This is a bit of an oversimplification since the level of difficulty of the questions may vary a little so that would still be a factor in the score, but at the higher reaches of the Verbal scoring spectrum the score really becomes much more about number of questions wrong. And to be at a really high Verbal score (90th percentile +) you really can’t have many questions wrong – maybe only a handful.
There are a few implications to be drawn from this. First of all, since you are likely to get a lot of questions wrong on the Quant section, it really does not make sense to spend undue time on questions that you are likely to get wrong anyway. Furthermore, running out of time at the end of the Quant section is not that big a deal (assuming that you actually select answers to all of the questions to not incur the unanswered questions penalty). Again, you are going to get a lot of questions wrong anyway so coming to question 19 with 2 minutes left and having to make some educated guesses on the last 3 or 4 questions will not impact your score that significantly.
On the Verbal section, on the other hand, you need to be much more careful about time management and not put yourself in a position of having to guess on the last 3 or 4 questions. That will impact your score more detrimentally, especially if you were tracking toward a really high score. If you had only 2 questions wrong up until question 18 and then had to guess on 18 through 23 and got 5 of those last 6 wrong for a total of 7 wrong on the Verbal section, that would be a big deal and would lower your score significantly.
Another upshot is that you need to be a little more certain of your answers on Verbal questions than on Quant questions. Most people probably feel like the opposite is what often happens since the nature of Verbal questions is that they feel ambiguous, but of course they are not and you need to be that much more rigorous in the way you choose your answers to ensure that you limit the educated guessing to a bare minimum. You just can’t afford to get Verbal questions wrong with the same frequency that you can Quant questions. What that means, practically speaking, is that you can’t run out of time on the Verbal section and that you need to choose answers because you KNOW they are right, not because you THINK they are right. That is obviously easier said then done, but see my post on The Principle of No Ambiguity for some more insight on that idea.
Knowledge is power and on the GMAT having a better understanding of the scoring algorithm is the kind of knowledge that helps lead to a better score. In a future post I am going to come back to the issue of pacing strategies on the Quant section so stay tuned!