Data Sufficiency – Where “No” Means “Affirmative”

(This is one of a series of GMAT tips that we offer on our blog.)

My hat is off to whomever created the Data Sufficiency question type, which holds within its format several delightfully crafty ways to elicit an incorrect answer. Perhaps none is more tricky and understated, however, than the method by which the test preys on our innate connection between the word “no” and its connotation of “negative”. (Author’s Note: This same connection was exploited recently-and-brilliantly on an episode of 30 Rock, in which Tracy Jordan exclaims that Jack’s medical test results were “positive” — meaning “good news” — because the actual results came back “negative”. But I digress…)

To illustrate, a Data Sufficiency question might ask:

Is x > 0?

A simple enough question, it would seem – is x positive – but then consider a potential first statement:

1) IxI = -x

This statement tells us that the absolute value of the number is equal to itself multiplied by negative one. Because of this, the number cannot be positive – any positive number multiplied by negative one becomes negative, but all absolute values are either positive or zero. A positive number simply cannot satisfy statement 1, and the answer to the overall question — Is x > 0? — is “no”.

Herein lies the rub — the answer to the question is “no,” which may lead you to believe that statement 1 is “negative” or “undesirable,” because of that connotation of the word “no” at which we just arrived. However, “no” is a definitive answer to the overall question. Given the information in statement one, we can prove one answer to that question, which means that “Statement (1) ALONE is sufficient”.

If you see, it would be easy, and somewhat intuitive, to “eliminate” statement 1 because it provided the answer “no”. But that’s not what Data Sufficiency questions ask — instead, they ask “do you have enough information to answer the question?”. Because of that, a definitive answer of “no” is, in fact, enough to answer the question, and so you must remind yourself that “no” means “sufficient”. To combat this common pitfall, I suggest writing the word “sufficient” at the top of your noteboard, and glancing at it each time you answer a Data Sufficiency question to remind yourself what the question is specifically asking.

Veritas Prep offers a full lesson on the Data Sufficiency question format, as well as hundreds of Data Sufficiency practice problems in its quantitative curriculum. For more information, please take a look at all of Veritas Prep’s GMAT preparation options.