|
Author |
Message |
|
TAGS:
|
|
|
Manager
Joined: 13 Apr 2008
Posts: 66
Followers: 1
Kudos [?]:
3
[0], given: 0
|
There is a set of number, the mean is m, the standard [#permalink]
 13 May 2008, 06:04
Question Stats:
0% (00:00) correct
 0% (00:00) wrong based on 0 sessions
There is a set of number, the mean is m, the standard deviation is R, if add a number x to this set, is x<=R?
1) x=m
2) m<x<m+R
Dont know the answer, please explain.
|
|
|
|
|
|
|
CEO
Joined: 17 Nov 2007
Posts: 3594
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 230
Kudos [?]:
1299
[0], given: 346
|
Re: DS- Standard Deviation [#permalink]
13 May 2008, 13:41
I guess E Consider two possible sets: first set: (-101,-100,-99): mean (m) is -100, standard deviation is about 1 second set: (99,100,101): mean (m) is 100, standard deviation is about 1 1. or 2. for first set x will be -100 or between -100 and -99 that are lesser than 1 for second set x will be 100 or between 100 and 101 that are greater than 1 1&2 are incompatible.
_________________
iOS/Android: GMAT ToolKit - The bestselling GMAT prep app | GMAT Club (free) | PrepGame | GRE ToolKit | LSAT ToolKit
PROMO: Are you an exiting GMAT ToolKit (iOS) user? Get GMAT ToolKit 2 (iOS) for free* (read more)
Math: GMAT Math Book ||| General: GMATTimer ||| Chicago Booth: Slide Presentation
The People Who Are Crazy Enough to Think They Can Change the World, Are the Ones Who Do.
|
|
|
|
|
|
Manager
Joined: 28 Sep 2007
Posts: 215
Followers: 1
Kudos [?]:
17
[0], given: 0
|
Re: DS- Standard Deviation [#permalink]
13 May 2008, 15:24
am i wrong here or do the statement contradict each other?
1)x=m
2)x<m
|
|
|
|
|
|
Manager
Joined: 12 Feb 2008
Posts: 186
Followers: 1
Kudos [?]:
33
[0], given: 0
|
Re: DS- Standard Deviation [#permalink]
13 May 2008, 17:00
this one doesn't make sense to me.
1 and 2 cannot have opposite assumptions!
|
|
|
|
|
|
Intern
Joined: 01 Jan 2007
Posts: 24
Followers: 0
Kudos [?]:
0
[0], given: 0
|
Re: DS- Standard Deviation [#permalink]
13 May 2008, 19:00
I presume statement A is true. When a no. which is equal to mean is added to the set, the std dev. does not change. I am lost with the second statement. please correct me if I am wrong.
_________________
Regards,
Rocky
|
|
|
|
|
|
Manager
Joined: 13 Apr 2008
Posts: 66
Followers: 1
Kudos [?]:
3
[0], given: 0
|
Re: DS- Standard Deviation [#permalink]
14 May 2008, 06:09
Value wrote: There is a set of number, the mean is m, the standard deviation is R, if add a number x to this set, is r<=R? ( r=std dev of new set)
1) x=m
2) m<x<m+R
Dont know the answer, please explain. Sorry Friends its r<=R not x<=R.
|
|
|
|
|
|
Manager
Joined: 11 Apr 2008
Posts: 157
Schools: Kellogg(A), Wharton(W), Columbia(D)
Followers: 1
Kudos [?]:
53
[0], given: 0
|
Re: DS- Standard Deviation [#permalink]
14 May 2008, 06:22
Value wrote: Value wrote: There is a set of number, the mean is m, the standard deviation is R, if add a number x to this set, is r<=R? ( r=std dev of new set)
1) x=m
2) m<x<m+R
Dont know the answer, please explain. Sorry Friends its r<=R not x<=R. Maybe you could edit the original post also. I did the whole thing before I read your correction. Thanks
|
|
|
|
|
|
Manager
Joined: 11 Apr 2008
Posts: 157
Schools: Kellogg(A), Wharton(W), Columbia(D)
Followers: 1
Kudos [?]:
53
[0], given: 0
|
Re: DS- Standard Deviation [#permalink]
14 May 2008, 06:28
With r<=R, I think its D.
Stt1: x=m, since x is exactly the mean it will leave the std. deviation unchanged. r=R. So the info is SUFF to answer.
Stt2: m<x<m+R => that x is larger than the mean. That means it is away from the center of the curve. So std. deviation must increase. (look at it like ( mean(x) - x(i) ) ^2 will add to the calcualtion of r). so r>R. So the info is SUFF to answer.
Thus, IMO: D
|
|
|
|
|
|
|
Re: DS- Standard Deviation
[#permalink]
14 May 2008, 06:28
|
|
|
|
|
|
|
|
|
|
|
close
