Understanding Data Sufficiency

Overview

A statement is sufficient if it provides enough information to answer the question being asked in such a way that you can be certain of a single answer to the question.

Sufficiency for Yes/No Questions

(See the explanation for what a yes/no question is)

For a statement to be sufficient, the information it provides must enable you to answer the question with a "yes" or "no" under all legitimate circumstances. If the information from the statement allows you enough leeway that you can sometimes answer the question "yes" while at other times you can answer "no", then the statement is not sufficient.

One common struggle new test-takers have with this question type is when they determine that the information from a statement allows you to answer the question "no" every time, they conclude that the information is not sufficient because the answer to the question is "no" instead of "yes." However, the key to sufficiency is not whether the answer is "yes" or "no," but that the information ensures that the same answer will be given every time.

Value Questions

(See the explanation for what a value question is)

A statement is sufficient if it provides information that ensures that the answer to the question is always one and only one number.

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