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Brian Galvin is the Director of Academic Programs at Veritas Prep, where he oversees all of the company’s GMAT preparation courses.
Though they will never admit to using “dirty tricks” to keep your score down, the authors of the GMAT can be shrewd in the way that they word questions to prey on the inefficiencies of human nature. Previously in this space, we talked about the “Simon Says” nature of Data Sufficiency questions, in which the authors know that you will often make assumptions about variables – that they are integers, or positive – without being explicitly told so. Data Sufficiency questions contain another, perhaps even more devilish, example of this need for perfect precision, embedded deeply in the way that these questions are written. Consider this fragment of a GMAT question:
Is x <0?
(1) x2 < x
Statement 1 tells us that x must be a positive number between 0 and 1: 0 < x < 1. More importantly to our purposes, statement 1 explicitly precludes all negative numbers as potential values for x. Any negative value of x, when squared, will become positive, meaning that x2 cannot be greater than a negative value of x. Accordingly, statement 1 tells us, emphatically, “NO” to the initial question, is x less than zero.
As human beings, we’re wired to take such an answer – “NO” – and eliminate statement one; “no” means “eliminate” in nearly all facets of our lives. But, much like a medical diagnosis, “negative” in this case is a positive thing. The fact that we get the definitive answer “NO” means that statement 1 did its job – it answered the question.
Look at just one of the Data Sufficiency answer choices:
A) Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient
The answer choices are precisely written for their purpose. Your job is to determine when you have enough information (when is the data sufficient?) to answer the overall question – NOT necessarily whether the answer is “yes”. The answer “no” to the question is, indeed, a definite answer, so the statement above, which provides that conclusive answer “no” is SUFFICIENT, and therefore we cannot eliminate answer choice A.
Remember that, on Data Sufficiency questions, the authors of the exam play to the inefficiencies in the way that we think. Be sure to recognize that you are prone to confusing “No” with “Insufficient”, and be ready to combat that. You may, for example, want to write the word “SUFFICIENT” at the top of your noteboard, just to remind yourself that your job on these questions is to test for sufficiency, and not for “correctness” (or any other term that would indicate “is the answer yes?”. Just like a negative diagnosis is a positive thing, so the answer “no” is sufficient for your purposes on test day. (And, think about it, if your doctor ever says “maybe”, well, that may be the worst answer of all.)
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