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Standard Deviation

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Junior | Next Rank: 30 Posts
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by Rohit21 » Wed May 02, 2012 2:24 pm
If set T consists of odd integers divisible by 5, is the standard deviation of T positive?

1. All members of T are positive
2. T consists of only one member

The answer is B. But how? Shouldn't the answer be D?
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Source: — Data Sufficiency |
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by aneesh.kg » Wed May 02, 2012 7:48 pm
Can Standard Deviation of a set of numbers ever be negative?
No.
Does it have to be positive always?
No.
What! Why?
Because it can be zero also.
When is it zero?
When all the numbers in a set are equal or there is just one number in the set.

Statement(1): We don't know if all members are equal.
INSUFFICIENT.
Statement(2): Only one member. Standard Deviation = 0.
So, the answer to the question is asked is a conclusive NO.
SUFFICIENT.

[spoiler](B)[/spoiler] is the answer.
Aneesh Bangia
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