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# A set of data consists of following 5 numbers : { 0, 2, 4,

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Manager
Joined: 28 Jul 2004
Posts: 135
Location: Melbourne
Schools: Yale SOM, Tuck, Ross, IESE, HEC, Johnson, Booth
A set of data consists of following 5 numbers : { 0, 2, 4,  [#permalink]

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26 Sep 2008, 09:26
A set of data consists of following 5 numbers : { 0, 2, 4, 6, 8}

What two numbers if added to create a set of 7 numbers, will result in a std deviation that is closest to the standard deviation for the set with just the original five numbers.

A. -1 and 9
B. 4 and 4
C. 3 and 5
D. 2 and 6
E. 0 and 8

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kris

Intern
Joined: 13 Jun 2008
Posts: 46

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26 Sep 2008, 09:34
OA is B

(4 and 4) same number and therefore the SD will not change because of adding them to the list of orginial 5
Manager
Joined: 15 Apr 2008
Posts: 159

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26 Sep 2008, 10:44
the standard deviation of the original set is 2.82 and that of the new set including number 3 and 5 is 2.44

so C is the closest in std deviation
SVP
Joined: 07 Nov 2007
Posts: 1728
Location: New York

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26 Sep 2008, 11:55
krishan wrote:
A set of data consists of following 5 numbers : { 0, 2, 4, 6, 8}

What two numbers if added to create a set of 7 numbers, will result in a std deviation that is closest to the standard deviation for the set with just the original five numbers.

A. -1 and 9
B. 4 and 4
C. 3 and 5
D. 2 and 6
E. 0 and 8

http://gmatclub.com/forum/7-t47858
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VP
Joined: 05 Jul 2008
Posts: 1329

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26 Sep 2008, 14:14
bdumpala wrote:
OA is B

(4 and 4) same number and therefore the SD will not change because of adding them to the list of orginial 5

Actually it changes because the denominator changes from 5 to 7. Worst traps we can imagine of on GMAT.

Agree with D.
Senior Manager
Joined: 04 Aug 2008
Posts: 362

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26 Sep 2008, 14:17
I thought they do not test st deviation formula? only basics like range etc

here, are you supposed to measure a range from median to the ends and thus figure out it should be the difference of 4?

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Re: Standard Deviation Problem &nbs [#permalink] 26 Sep 2008, 14:17
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# A set of data consists of following 5 numbers : { 0, 2, 4,

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