The Logic of GMAT Data Sufficiency

I recently received an e-mail from someone undergoing a mini-crisis over GMAT Data Sufficiency. I’ve decided to share the e-mail and my thoughts with the GMAT world:

“… so critical reasoning isn’t much of a problem, nor is problem solving. But I can’t, for the life of me, wrap my mind around data sufficiency. And, really, I don’t understand why it appears on the GMAT. Is it there to torture us? Did a bunch of evil GMAT people gather around a table and look for the best way to torment people who want to go to business school?”

This and similar sentiments are common among many test-takers. When you encounter a question-type as unorthodox as GMAT Data Sufficiency, it’s difficult to come up with a cogent explanation for its existence. After all, aren’t GMAT Problem Solving questions sufficient to test a person’s quantitative abilities?

To understand why Data Sufficiency appears on the GMAT and why it is in fact a useful measure of a person’s future success in the business world, we need to first understand the unique construction of GMAT Data Sufficiency questions and what they’re testing.

Unlike the problem solving questions you’re used to, Data sufficiency questions aren’t concerned with your ability to answer a question; instead, they’re concerned with your ability to determine whether a question CAN be answered. Though some of the abilities necessary to do well in problem-solving certainly transfer over to Data sufficiency (such as doing quick arithmetic and finding shortcuts to determine a solution), GMAT Data Sufficiency is much more concerned with your “meta-reasoning”– your ability to view an issue from the top-down and understand the essence of a complex situation. This last point is an essential one, and it provides insight into why Data Sufficiency appears on the GMAT.

If you’re the CEO or COO of a corporation, you won’t be able to accomplish every task for your organization. Instead, you’ll be expected to develop plans of action and to subsequently delegate those responsibilities to people who must “report” to you. Determining how to structure and execute a plan and whether such a plan can even be realized will require several important traits:

#1: The ability to quickly distill the essential issue in a problem.
#2: The ability to determine whether the information available to you is sufficient for properly addressing a problem.
#3: The ability to predict what additional information will be necessary to solve that problem

Notice that all of these skills overlap significantly with the skills necessary to do well on Data Sufficiency. Point #1 correlates to “re-phrasing” the question stem in Data Sufficiency (e.g. If the question asks: “Is the integer x divisible by 15? you could re-phrase it to ask: “Does x have 5 and 3 as prime factors?). Point #2 is the very issue at hand in Data Sufficiency: Figuring out if the information in the statements is sufficient to answer the question. And point #3 corresponds to the skills you’ll need to determine what information is lacking in a certain statement.

Of course, you could argue that all of this theorizing is strictly academic and that knowing why Data Sufficiency questions exist won’t tell you much about how to solve them. It’s my personal belief, though, that besting a test as nuanced as the GMAT requires a thorough understanding of the test-maker’s logic. Knowing the reason that Data Sufficiency questions exist should ultimately help you understand the best way to approach them.