A certain list of 100 data has an average (arithmetic mean)

Oldest

Best Reply

Author

Message

TAGS:

Intern

Joined: 26 Feb 2008

Posts: 37

Followers: 0

Kudos [?]: 7 [0], given: 0

A certain list of 100 data has an average (arithmetic mean) [#permalink]

22 Mar 2008, 17:17

00:00

Question Stats:

0% (00:00) correct

0% (00:00) wrong

based on 0 sessions

A certain list of 100 data has an average (arithmetic mean) 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 standard deviation less than d?

(A) -6 & 0
(B) 0 & 0
(C) 0 & 6
(D) 0 & 12
(E) 6 & 6

Pls explain. Thanks.

Senior Manager

Joined: 15 Aug 2007

Posts: 257

Schools: Chicago Booth

Followers: 1

Kudos [?]: 36 [0], given: 0

Re: PS:Standard Deviation [#permalink]

22 Mar 2008, 19:02

E - Same question was posted a day ago. SD depends on the deviation from mean, so for values in E the deviations are zero which is the minimum we can get.

SVP

Joined: 04 May 2006

Posts: 1946

Schools: CBS, Kellogg

Followers: 10

Kudos [?]: 168 [0], given: 1

Re: PS:Standard Deviation [#permalink]

22 Mar 2008, 19:59

sreehari wrote:

E - Same question was posted a day ago. SD depends on the deviation from mean, so for values in E the deviations are zero which is the minimum we can get.

Sorry guys, can you give more discription? Why "values in E the deviations are zero" make the new SD less than the old?
_________________

Find out what's new at GMAT Club - latest features and updates

Manager

Joined: 02 Mar 2008

Posts: 213

Concentration: Finance, Strategy

Schools: Wharton '14 (D), Booth '14 (D), Sloan '14 (D), CBS '14 (D), Tuck '14 (WL), Darden '14 (A)

Followers: 1

Kudos [?]: 36 [0], given: 1

Re: PS:Standard Deviation [#permalink]

22 Mar 2008, 20:07

add 6 to the population of mean 6 does not change it mean
so the 2 new squares of difference are 0 -> reduce ur SD (divide by N+2)

SVP

Joined: 04 May 2006

Posts: 1946

Schools: CBS, Kellogg

Followers: 10

Kudos [?]: 168 [0], given: 1

Re: PS:Standard Deviation [#permalink]

22 Mar 2008, 20:19

AlbertNTN wrote:

add 6 to the population of mean 6 does not change it mean
so the 2 new squares of difference are 0 -> reduce ur SD (divide by N+2)

Thank you,

I plan to make a stupid calculation.
:oops:

_________________

Find out what's new at GMAT Club - latest features and updates

Re: PS:Standard Deviation [#permalink] 22 Mar 2008, 20:19

		Similar topics	Author	Replies	Last post
Similar Topics:		A certain list of 100 data has an average (arithmetic mean)	ffgmat	4	22 May 2006, 05:03
		A certain list of 100 data has an average (arithmetic mean)	shehreenquayyum	3	04 Nov 2006, 19:48
		A certain list of 100 data has an average (arithmetic mean)	jp888	1	28 Aug 2007, 06:12
		A certain list of 100 data has an avarage (arithmetic mean)	Snayt	3	22 Mar 2008, 04:58
	3	A certain list of 100 data has an average (arithmetic mean)	Gmatter111	5	08 Dec 2009, 03:54

A certain list of 100 data has an average (arithmetic mean)

Main navigation

GMAT Resources

Partners

MBA Resources

GMAT ® is a registered trademark of the Graduate Management Admission Council ® (GMAC ®). GMAT Club's website has not been reviewed or endorsed by GMAC.

GMAT Courses

Admissions Consulting

A certain list of 100 data has an average (arithmetic mean)

A certain list of 100 data has an average (arithmetic mean)

Main navigation

GMAT Resources

Partners

MBA Resources