Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

If m is the arithmetic mean (average) of 4 integers a, b, c, and d and s is the standard deviation of the 4 integers, then is s > 0?

(1) m > a

(2) a + b + c + d = 0

When you modify the original condition, the question s>0? means if there is any other number since all the number are the same when s=0. For 1), from m>a, (a+b+c+d)/4>a, a+b+c+d>4a, b+c+d>3a. From b+c+d>a+a+a, it means that at least one pair is different in a,b,c,d, which is yes and sufficient.

Therefore, the answer is A.

Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.

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