# Data Sufficiency Question Types

Although the format of each data sufficiency question is the same (i.e., the same five answers always exist) and the overall concept is always the same (i.e., determining whether Statements (1) and/or (2) provide sufficient information to answer the question), there are two types of data sufficiency questions. Note that this differentiation is one that we make. When you take the GMAT, you will not be told whether a problem is a yes/no or value question. However, the ability to differentiate between these two question types is an extremely valuable tool in mastering data sufficiency.

## Yes/No Questions

Yes/No Questions ask a question that needs to be answered with "yes" or "no" (hence the name of the question type). In this problem type, for a statement to be sufficient, the information it provides must enable you to answer definitively the question with "yes" or "no" every time. In other words, a statement is not sufficient if you can answer "no" or "yes." Note that even if your answer is "no," as long as the information provided in the statement is sufficient to answer "no" every time, the statement is sufficient. Consider the following example: (Note that a real GMAT question would never be this easy. However, this question is constructed to help elucidate the problem type and format.)

- x > 10
- x < 14

**B**

- In order for a statement to be sufficient, it must definitively answer the question (i.e., it must definitively indicate whether x > 15?) For sufficiency to exist, the information in the statement must allow you to answer the question with the same answer every time (either "yes" or "no). The key is not whether the answer is "yes" or "no", but whether the information allows you to answer the same way each time.
- Statement (1) indicates that x > 10. So, x could be 11, 12, 13, 14, 15, 16, 17...
- Since x could be 11, in which case it would not be greater than 15 and the answer to the origial question would be "no", or x could be 17, in which case it would be greater than 15 and the answer to the original question would be "yes", Statement (1) is NOT SUFFICIENT.
- Statement (2) indicates that x < 14. So, x could be 13, 12, 11, 10, 9... Since all the possible values of x permissible by Statement (2) allow you to answer "no" to the question, Statement (2) is SUFFICIENT.

*Work additional data sufficiency practice questions.*

## Value Questions

Value Questions ask a question that needs to be answered with a definitive value. In this type of question, for a statement to be sufficient, the information it provides must enable you to answer definitively the question with a specific unique value. In other words, a statement is not sufficient if you can answer 5 sometimes or -5 other times. This type of data sufficiency question is the most common. Consider the following example:

^{2}+ y?

- x = 4
- y
^{2}= 16

**E**

^{2}+ y can be found.

- In order for a statement to be sufficient, the data from the statement must ensure that there is one-and-only-one value for the expression x
^{2}+ y. If there are multiple possible values for this expression, then the statement is not sufficient. - Evaluating Statement (1), we can substitute and write the equation: 4
^{2}+ y. However, this is not sufficient because if y = 0, x^{2}+ y = 4^{2}+ 0 = 16 but if y = 1, x^{2}+ y = 4^{2}+ 1 = 17. Since there are two possible legitimate values for the expression given the information from Statement (1), Statement (1) is NOT SUFFICIENT. - Evaluating Statement (2), we know that y is 4 or -4. We know now that the equation is x
^{2}+ 4 or x^{2}- 4. However, this statement is not sufficient because if x = 0, the equation could evaluate to 0^{2}+ 4 = 4 or 0^{2}- 4 = -4. Since the information from Statement (2) does not allow us to determine one value for the expression, Statement (2) is NOT SUFFICIENT. - When examining Statement (1) and (2) together, we know that the x = 4 and y = 4 or -4. However, these two statements are not sufficient because the expression could evaluate to 4
^{2}+ 4 = 20 or 4^{2}- 4 = 12. Statements (1) and (2), even when taken together, are NOT SUFFICIENT.

*Work additional data sufficiency practice questions.*