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# m05#07

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Manager
Joined: 14 May 2008
Posts: 57

Kudos [?]: 16 [1], given: 1

Schools: Wharton (WEMBA East)

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14 Oct 2008, 19:12
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Which of the following sets has the standard deviation greater than the standard deviation of set X={-19, -17, -15, -13, -11}

I. A={1, 3, 5, 7, 9}

II. B={2, 4, 6, 8, 10}

III. C={1, -1, -3, -5, -7}

A. Set A only
B. Set B only
C. Set C only
D. Sets A, B and C
E. None of the sets

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Last edited by Bunuel on 14 Nov 2013, 07:21, edited 1 time in total.
Updated

Kudos [?]: 16 [1], given: 1

Math Expert
Joined: 02 Sep 2009
Posts: 41871

Kudos [?]: 128526 [4], given: 12180

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19 Nov 2012, 07:55
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scorcho wrote:
Which set has the greatest standard deviation?

I. 1, 3, 5, 7, 9
II. 2, 4, 6, 8, 10
III. 1, -1, -3, -5, -7

(A) I
(B) II
(C) III
(D) I and II
(E) none

[Reveal] Spoiler: OA
E

Source: GMAT Club Tests - hardest GMAT questions

Current explanation implies one would calculate the stddev for the sequence.

Alternate explanation: They're all just skip+1 sets of the form f(n)=kn+x, k=2, no need to calculate stddev.

BELOW IS REVISED VERSION OF THIS QUESTION:

Which of the following sets has the standard deviation greater than the standard deviation of set X={-19, -17, -15, -13, -11}

I. A={1, 3, 5, 7, 9}

II. B={2, 4, 6, 8, 10}

III. C={1, -1, -3, -5, -7}

A. Set A only
B. Set B only
C. Set C only
D. Sets A, B and C
E. None of the sets

If we add or subtract a constant to each term in a set the standard deviation will not change.

Since each set can be obtained by adding some constant to each term of set X (20 for set A, 21 for set B and 12 for set C), then the standard deviations of all sets are the same.

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Kudos [?]: 128526 [4], given: 12180

Manager
Joined: 07 May 2013
Posts: 108

Kudos [?]: 30 [0], given: 1

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22 Nov 2013, 14:44
Buneul, the concept of standard deviation is alien to many including me. Can please post a link to a page explaining this concept in detail.

Kudos [?]: 30 [0], given: 1

Math Expert
Joined: 02 Sep 2009
Posts: 41871

Kudos [?]: 128526 [0], given: 12180

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22 Nov 2013, 14:45
Buneul, the concept of standard deviation is alien to many including me. Can please post a link to a page explaining this concept in detail.

Theory on Statistics and Sets problems: math-standard-deviation-87905.html

All DS Statistics and Sets problems to practice: search.php?search_id=tag&tag_id=34
All PS Statistics and Sets problems to practice: search.php?search_id=tag&tag_id=55

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Kudos [?]: 128526 [0], given: 12180

Re: m05#07   [#permalink] 22 Nov 2013, 14:45
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# m05#07

Moderator: Bunuel

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