SD : GMAT Data Sufficiency (DS)
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# SD

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Intern
Joined: 18 May 2011
Posts: 17
Followers: 0

Kudos [?]: 1 [1] , given: 13

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29 May 2011, 10:16
1
KUDOS
00:00

Difficulty:

(N/A)

Question Stats:

86% (01:36) correct 14% (00:40) wrong based on 7 sessions

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Hi All,

Thanks!
[Reveal] Spoiler: OA

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question.JPG [ 66.85 KiB | Viewed 1422 times ]

Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2021
Followers: 162

Kudos [?]: 1743 [0], given: 376

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29 May 2011, 11:38
Carol680 wrote:
Hi All,

Thanks!

Refer:
gmat-prep-ds-q-94166.html
math-standard-deviation-87905.html
_________________
Intern
Joined: 18 May 2011
Posts: 17
Followers: 0

Kudos [?]: 1 [0], given: 13

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01 Jun 2011, 01:57
thangduong wrote:
it is best to remember the formular of the SD= square of (1/n (a1-x)^2 + (a2-x)^2+.........)

from 1, now we replace a1 with 0.7 a1, x with 0.7 x as condition 1 tell us. Every thing reduce to 0.7

it is clear we can find new SD. DONT COUNT, just know it is sufficient.

from 2, we can not know the square of diffence between each number and average in the new set. not sufficient.

thank you very much
Re: SD   [#permalink] 01 Jun 2011, 01:57
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