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A certain characteristic in a large population has a

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A certain characteristic in a large population has a [#permalink] New post 08 Oct 2008, 12:07
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

A certain characteristic in a large population has a distribution that is symmetric about the mean m. If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d ?

A. 16%
B. 32%
C. 48%
D. 84%
E. 92%
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Re: math---mean [#permalink] New post 08 Oct 2008, 12:08
albany09 wrote:
A certain characteristic in a large population has a distribution that is symmetric about the mean m. If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d ?

A. 16%
B. 32%
C. 48%
D. 84%
E. 92%



= .5 + .68/2
= .84 or 84%
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Re: math---mean [#permalink] New post 08 Oct 2008, 12:12
GMATTiger .... please explain ..
I did not understand it ?
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Re: math---mean [#permalink] New post 09 Oct 2008, 08:28
guttal007 wrote:
GMATTiger .... please explain ..
I did not understand it ?


68% is + or - 1SD from the mean. Since it is ND, 68% lies equally to the left and right of the mean. So it is 50% plus 34% and is 84%.
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Re: math---mean [#permalink] New post 09 Oct 2008, 08:36
albany09 wrote:
A certain characteristic in a large population has a distribution that is symmetric about the mean m. If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d ?

A. 16%
B. 32%
C. 48%
D. 84%
E. 92%


Draw a bell curve. Divide this curve into 4 sections: Left, Middle left, Middle right, and Right.

From the question.
Middle left + Middle right = 68%
Therefore, Left + Right = 100% - 68% = 32%
Left = Right
Left = 16%
Right = 16%

The question wants to know the area of (Left + Middle left + Middle Right) = 16% + 68% = 84%

The answer is D.
Re: math---mean   [#permalink] 09 Oct 2008, 08:36
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