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# Source: GMATPrep A certain list of 100 data has an average

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Joined: 30 Jun 2008
Posts: 1026
Source: GMATPrep A certain list of 100 data has an average [#permalink]

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11 Oct 2008, 05:35
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Source: GMATPrep

A certain list of 100 data has an average of 6 and a standard deviation of d, where d is positive. Which of the following pairs of data, when added to the list, must result in a list of 102 data with a SD less than d?

a) -6 and 0
b) 0 and 0
c) 0 and 6
d) 0 and 12
e) 6 and 6

Please explain.
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Senior Manager
Joined: 21 Apr 2008
Posts: 269
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Re: PS : GMATPrep - Standard Deviation [#permalink]

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11 Oct 2008, 06:02
E

SD decreases as the values get more closer the mean, so by adding 6 and 6, we reduce the SD to less than d
Re: PS : GMATPrep - Standard Deviation   [#permalink] 11 Oct 2008, 06:02
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# Source: GMATPrep A certain list of 100 data has an average

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