Data Sufficiency (DS) questions are unique to the GMAT. When first encountered they are cumbersome, confusing, and generally frustrating. Admittedly, Data Sufficiency questions often remain cumbersome, confusing, and generally frustrating, but such is the nature of the GMAT. After all, the better you do, the harder the test gets! However, thorough understanding of the characteristics and attributes of these questions coupled with a proven method of attack will allow you to handle just about anything the GMAT has to offer. In this blog entry, I will offer some GMAT Data Sufficiency tips to help you master this challenging question type.
The prescribed task for Data Sufficiency questions is straightforward enough: based on provided information, determine whether a posed question can be answered. The structure of these questions is unwaveringly consistent: a question is asked, two statements of additional information are provided, and the five answer choices that follow are always the same (I’ll discuss those later).
Data Sufficiency (DS) questions come in two types: Value and Yes/No.
- A Value DS question asks for a numerical value (e.g., What is the value of x?). For information to be considered sufficient, that information must allow us to deduce only one value for x.
- Yes/No DS questions (e.g., Is x odd?) merely want one of those answers, either of which is acceptable.
For Yes/No DS questions, it is that last bit that presents somewhat of a dogleg in the conceptual understanding of this type. Simply put, test takers must recognize and accept that “no” is a sufficient answer. Consider the presented example “Is x odd?” Now, if, through the provided information, we learn that x is not odd and instead x is even, then we would be able to answer the question. The answer would be, “No. x is not odd. x is even.” Answering the question is all we need to be able to do.
Let’s keep with the example for a moment longer. A very common misstep would be that, after learning x is definitively even, a person then concludes the provided information is insufficient. But why? We answered the question, didn’t we? Remember: if you can unequivocally answer a Yes/No DS question with either a “yes” or a “no,” you’ve got sufficiency. Insufficiency is the result of information that, when evaluated, culminates in a “sometimes yes” and/or a “sometimes no” response. Sometimes is not good enough. Always is mandatory.
GMAT Data Sufficiency Strategy
As with every question format on the GMAT, you must have a proven step-by-step methodical approach. Do this for every Data Sufficiency question:
- Analyze the Question [This first step consists of three separate parts.]
- Determine if it is a Value or Yes/No question type.
- Simplify the question. [For example, if the question is “What is the value of m if n = 3t – 2m?” then you would rearrange the given equation in the form of m = (3t –n)/2 since the question asks about m.]
- Identify what information, if it were provided, would be sufficient to answer the question. [In the above example, we would look for values of t and n, two additional equations using these variables, or a value for the expression (3t –n)/2.]
- Evaluate the statements (aka, the provided information) using 12TEN. [I’ll break down what 12TEN stands for in the answer choice discussion below.]
Note what happens when using the Kaplan Method for Data Sufficiency: you do a lot of work before you look at the statements. Such an approach is essential if you truly want to beat GMAT DS questions.
Data Sufficiency Answer Choices
Now, let’s consider the answer choices. As stated, the five answer choices for DS questions are always the same. Step 2 of the Kaplan Method for Data Sufficiency uses a handy mnemonic that helps keep those answer choices straight as well as ensures you assess the statements in the proper order. Here’s the breakdown:
(1) The first statement provides enough information to answer by itself, but the second statement does not;
(2) The second statement provides enough information to answer by itself, but the first statement does not;
(T) Only when the two statements are considered together does one have sufficient information to answer the question;
(E) Either statement provides enough information to answer the question when considered individually;
(N) Neither statement, when considered alone or together, provides sufficient information to answer the question. Additional information is necessary.
As per the answer choices as well as Kaplan’s mnemonic, it is imperative that you evaluate the two statements individually before assessing them together. After evaluating Statement 1, regardless of whether it was sufficient or insufficient to answer the question, you must pretend as if you never saw it when you take a look at Statement 2. The only time you use the information in both statements together is if each individually were found to be insufficient on their own. At that point, you are only deciding between answer choices T and N.
Now you've learned the nuts and bolts of GMAT Data Sufficiency. Keep this blog post open and use it to work through a handful of DS practice questions.
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