hemanthp wrote:
A Bell Curve (Normal Distribution) has a mean of − 1 and a standard deviation of 1/8 . How many integer values are within three standard deviations of the mean?
A. 0
B. 1
C. 3
D. 6
E. 7
As Zoser above was saying, this question makes no sense. If a question says "a list has a mean of -1 and a standard deviation of 1/8, how many integer values are within 3 standard deviations of the mean?" that question does not mean "how many integers are between -1 - 3/8 and -1 + 3/8" (or between -1.375 and -0.625). It means "how many values in the set or distribution are integers that are between -1.375 and -0.625?". So if our set is
-9/8, -9/8, -9/8, -7/8, -7/8, -7/8
the answer would be 'zero', and if the set were instead
-1.25, -1, -1, -1, -1, -1, -1, -0.75
the answer would be 'six', because six values (all of the values equal to -1) are between -1.375 and -0.625.
So we need to know about our list or set to answer this question. And you don't need to know anything at all about "normal distributions" on the GMAT, but if you do know about those distributions, you'll know they're infinite continuous distributions. And in a continuous distribution, the number of values in the distribution equal to any one specific number is zero. So that's the answer a statistician would give here, but that statistician would be using knowledge miles beyond the scope of the GMAT.
The question writer means to ask "how many distinct integers are there between -1.375 and -0.625", and the answer to that question is 'one', but that's not what this question is actually asking.
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