Quick question about Data Sufficiency rule

[gameson]

I have a question.

Lets say the question is asking wheter a number is an odd integer, or whether x > y, something like that

then in statement 1, it shows a clue that statement 1 is giving enough information to answer the question, BUT the answer is wrong (i.e if the Q is asking if it's an odd integer, then in statement 1, it's sufficient to answer the Q but the answer is an even integer. Does it mean statement 1 is sufficient? another example is Q is whether x > y. Statement 1 is giving enough clue but the answer is x < y)

My understanding is that if the statement is giving enough clue but answering it wrong, so it means it's sufficient enough.

BUT i m practicing using the official GMAT review, and it says otherwise. When the answer is wrong, that means the statement is not sufficient.

I am confused....

[2008]

there are 2 kind of questions in data sufficiency:

- the one that ask to find the result/number of a problem
- the one where you have to answer YES or NO

the way i approach it is that if it is a YES or NO one i write Y N at the top of my notebook. it's very helpful.

once u ve actually determined this then the DS questions are about "do you have sufficient data to: find the result/answer YES or NO" ?

in the first case if you have sufficient data to find the number, then is ok

in the second case you need sufficient data either for answering Y or for answering NO. but once you have sufficient data, no matter if for saying Y or N, then is ok.

both in the first and in the second case, it is NOT ok when you DONT have sufficient data to give an answer


getting back to the way you posed the problem, your "understanding" is right



i'm sure you can find much better of answers than mine in this forum and googling GMAT DATA SUFFICIENCY

[Ian Stewart]

BUT i m practicing using the official GMAT review, and it says otherwise. When the answer is wrong, that means the statement is not sufficient.

I'm curious- where did you read that?

On DS, your task is to determine whether the statements give you enough information to give a definite answer to the question. It doesn't matter if the answer to the question is 'yes' or 'no', just as long as you can be 100% certain of the answer. That said, it is very rare to find a real GMAT DS question where you have sufficient information for a yes/no question, but the answer turns out to be 'no', so you probably won't need to worry about this. There is, for example, only one such question in the Official Guide.

[gameson]

Thanks for the reply, Ian. I read that exactly from the GMAT Official Review as the Official is the only practice test that I try so far, and it pissed me off. It's sufficient enough for an answer and it's a NO, but the answer says not sufficient because the answer is wrong. I don't remember the question number, but it has brought to my attention.

[erjamit]

@Ian

There is, for example, only one such question in the Official Guide.

Can you pls tell which question you are talking about.

Thanks
Amit

[Ian Stewart]

Question 89, in the Orange OG, 11th Ed. Of the 55 yes/no DS questions in the OG for which E is not the right answer, it's the only one where the statements answer a yes/no question with a 'no'.