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Your Data Sufficiency Isn’t Sufficient

Last month, I highlighted the idea that “you don’t deserve a 700+” on the GMAT. And the response has been positive, as negative as the title of the article might sound. Many students have been happy to hear the truth, that to score among the top 10% of an exclusively high-achieving pool of examinees will take some ingenuity and a little more than just “studying the content.” So this month let’s explore another related truth: what you know about data sufficiency probably isn’t sufficient.

Again, let’s start with the understanding that to even consider taking the GMAT requires a high bar of academic success. Those taking the GMAT have not only been to college, but were successful enough there that they feel capable of even-higher education, and have usually been successful enough in the workplace, too, that they find business school to be the ideal next step. You’re competing against an elite pool – much like everyone competing in an event at the Olympics has already met the fundamental standard of being among the best in their country, everyone taking the GMAT has done well enough on previous exams – standardized and not – that they “qualify” to take the GMAT. To score at or above 700 you need to “beat” 90% of those other test-takers.  The competition is stiff!

Which is why it can be frustrating to watch those 700+ aspirants talk about their so-called Data Sufficiency mastery.  Many feel as though knowing these things about Data Sufficiency is sufficient to make them successful:

*The answer choices are fixed

*They can use process of elimination via a mnemonic device to remember the answers (AD/BCE split for statement one; 1-2-T-E-N to remember the meaning of the choices in order)

*When you answer for statement 1, you have to make sure that you then forget that information so that you assess statement 2 ALONE.

*If you know that your algebra will produce an answer, you don’t need to complete the math because you’ve already proven that the data is sufficient.

Voila – 700 here you come.  Right?

Here’s the problem – that’s not really that much to master, at least if your goal is to be better at Data Sufficiency than 75-80% of the rest of the field and therefore have a shot at being top 10% on the test overall. While it’s certainly true that many test-takers sit for the GMAT without having mastered the above, at least half of your competition has. If your goal is to be in the top 10%, it’s simply not sufficient to feel complacent about your knowledge base if more than 50% of your competition shares it with you.

So what can you do? Learn to master the “game” of Data Sufficiency, which is just as much a logic puzzle / strategy game as it is a math question. Consider, for example, the question:

Set J consists of the terms {2, 7, 10, 12, a}.  Is integer a > 7?

(1) a is the median of Set J

(2) Set J does not have a mode

Now, if you answer that Set J is sufficient, you’re far from alone. Of the examinees who will score around average or above, most will say “Sufficient” with you (and all the way at the lower end of the scale, you may find that many don’t understand the concept of a median or of Data Sufficiency, but if you’re reading this you’re not too worried about competing with those folks). Here’s likely your mode of thinking – if a is the median – the middle number, then you’d situate it as the third term:  2, 7, a, 10, 12. So clearly a is between 7 and 10, and therefore it’s greater than 7.

Or is it?

Statement 2 is clearly not sufficient. It offers no insight as to the value of a.  So why is it there?  It tells you that there are no repeat values in Set J – there is no “most frequently occurring number” – so a cannot equal 2, 10, 12, or most importantly 7. And this is crucial, because think back to your assessment of statement 1 – did you consider that a could be 7? If so, the sequence would go:  2, 7, 7 (this is a), 10, 12.  a is the median…but it’s also not greater than 7.  So we have an answer of “no” to pair with our answer of “yes” from previously.  As it turns out, statement 1 is NOT sufficient.