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standard deviation

by success1111 » Thu Apr 30, 2009 8:12 pm
A scientist recorded the number of eggs in each of 10 birds’ nests. What was the standard deviation of the numbers of eggs in the 10 nests?

(1) The average (arithmetic mean) number of eggs for the 10 nests was 4.
(2) Each of the 10 nests contained the same number of eggs.
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Re: standard deviation

by Vemuri » Thu Apr 30, 2009 8:29 pm
IMO B

Standard deviation is a statistically derived specified distance from the mean.

Stmt 1: Tells us that the mean is 4. Its not sufficient to tell what the standard deviation will be (we don't have to calculate SD in GMAT, even in PS questions)

Stmt 2: Tells us that each of the nests have the same number of eggs. That means, the mean value is the same & there is no deviation. So, the standard deviation is 0 (zero). Hence this statement is sufficient to answer the question.
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Re: standard deviation

by success1111 » Thu Apr 30, 2009 8:48 pm
Vemuri wrote:IMO B

Standard deviation is a statistically derived specified distance from the mean.

Stmt 1: Tells us that the mean is 4. Its not sufficient to tell what the standard deviation will be (we don't have to calculate SD in GMAT, even in PS questions)

Stmt 2: Tells us that each of the nests have the same number of eggs. That means, the mean value is the same & there is no deviation. So, the standard deviation is 0 (zero). Hence this statement is sufficient to answer the question.
Thanks. OA is B.
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by aj5105 » Fri May 15, 2009 3:04 am
(B)
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