This tests the quantitative reasoning ability using an unusual set of directions. The examinee is given a question with two associated statements that provide information that might be useful in answering the question. The examinee must then determine whether either statement alone is sufficient to answer the question; whether both are needed to answer the question; or whether there is not enough information given to answer the question. Data sufficiency is a unique type of math question created especially for the GMAT. Each item consists of the questions itself followed by two numbered statements.
(A) If statement 1 alone is sufficient to answer the question, but statement 2 alone is not sufficient.
(B) If statement 2 alone is sufficient to answer the question, but statement 1 alone is not sufficient.
(C) If both statements together are needed to answer the question, but neither statement alone is sufficient.
(D) If either statement by itself is sufficient to answer the question.
(E) If not enough facts are given to answer the question.
Perhaps the easiest way to fully internalize the scope of these questions is to replace the word “is” with the words “must be” – the questions are not asking whether an answer is possible, but rather, whether it “must” be the case