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Re: Each term of set T is a multiple of 5, is the standard deviation of [#permalink]
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Ans is B

1) If pos nos are 5 10 15 the SD>0
If pos nos are same 15 15 15 SD= 0

SD=0 or SD>0

2) Only one number SD= 0
Hence suff to say SD is not greater than zero . SUFFICIENT
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Re: Each term of set T is a multiple of 5, is the standard deviation of [#permalink]
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Jivana wrote:
Each term of set T is a multiple of 5. Is standard deviation of T positive?

(1) Each term of set T is positive
(2) Set T consists of one term




SD in layman terms is the distance between each term and the mean of the set

Given: Each term of the set is a multiple of 5
Required: SD of the set > 0?

Statement 1: Each term of the set is positive
There can be various versions of this set
Set 1: {5, 10, 15}
In this case, SD = 5 (Distance of the elements of the set from the mean)
Set 2: {5, 5, 5}
In this case, SD = 0 (Distance of the elements of the set from the mean)
No unique value of SD

INSUFFICIENT

Statement 2: Set T consists of one term
If there is only one element in the set, then SD = 0
Hence we have a unique value of SD

SUFFICIENT

Correct Answer B
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Re: Each term of set T is a multiple of 5, is the standard deviation of [#permalink]
SD in each case is positive then why the answer is not "D"?­ Bunuel
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Re: Each term of set T is a multiple of 5, is the standard deviation of [#permalink]
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curiousPope wrote:
SD in each case is positive then why the answer is not "D"?­ Bunuel

­
The SD is not always positive it can also be 0. Your doubt is addressed in the solution above. Please review carefully. 
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Re: Each term of set T is a multiple of 5, is the standard deviation of [#permalink]
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