Hi richachampion,

This DS question is more of a 'conceptual' question than anything else. The Standard Deviation of a group of numbers will always be positive UNLESS every number in the group is the same (in which case the Standard Deviation will be 0).

We're told that all of the numbers in Set T are even integers that are multiples of 3. We're asked if the SD is POSITIVE. This is a YES/NO question.

1) All elements of set T are positive

IF.... Set T = {6, 12} then the answer to the question is YES.
IF... Set T = {6, 6} then the answer to the question is NO.
Fact 1 is INSUFFICIENT

2) The range of set T is 0

Since the range is 0, then all of the numbers in Set T must be the SAME number. Thus, the SD is 0 and the answer to the question is ALWAYS NO.
Fact 2 is SUFFICIENT

Final Answer: B

GMAT assassins aren't born, they're made,
Rich