mgmat 6

I haven't read anything re: official policy, though I think that would be a good policy to have - but I do know that GMAT Focus does simply use questions that have been retired from the official pool.

I think my first post to this thread came at the end of a long day- on reflection, I could have phrased my comments more diplomatically. In any case, what is certainly true:

-if you ever encounter a yes/no DS question, and one statement guarantees the answer to the question is 'no', then that statement is certainly 'sufficient' to answer the question;

-there are 64 yes/no DS questions published in the orange Official Guide. Of these, 9 yield an answer of E. Of the remaining 55 questions for which there is sufficient information, in 54 cases the answer turns out to be 'yes'. Question 89 is the lone exception.

I've also yet to see a DS question in GMATPrep for which the statements conclusively yield a 'no' answer. If such questions are still around, they're rare.