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Sets A, B and C are shown below. If number 100 is included in each of

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Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 23 Nov 2011, 13:00
1
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

74% (00:51) correct 26% (00:45) wrong based on 56 sessions

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Sets A, B and C are shown below. If number 100 is included in each of these sets, which of the following represents the correct ordering of the sets in terms of the absolute increase in their standard deviation, from largest to smallest?

A {30, 50, 70, 90, 110}, B {-20, -10, 0, 10, 20}, C {30, 35, 40, 45, 50}

(A) A, C, B
(B) A, B, C
(C) C, A, B
(D) B, A, C
(E) B, C, A

Any idea how to solve these guys please? And what will be the answer? OA is not provided. Also, can GMAT ask to calculate the SD?

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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 23 Nov 2011, 14:28
B) ABC
you dont even need to calculate anything
it is easy...the smaller the range between numbers, the smaller the Standard Deviation and vice versa, the larger the difference or the range between numbers the larger the SD

hope this helps
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 23 Nov 2011, 14:30
1
and the GMAT will never ask u a question about SD where you have to calculate the SD because the formula is too cumbersome...most of SD question is the one above..
good luck and if you have any question, do not hesitate to ask
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 23 Nov 2011, 20:10
manalq8 wrote:
B) ABC
you dont even need to calculate anything
it is easy...the smaller the range between numbers, the smaller the Standard Deviation and vice versa, the larger the difference or the range between numbers the larger the SD

hope this helps


I dont think increase in the standard deviation depends on the range ..

The more is distance of 100 from the mean of each set, the more increase is going to be there in standard deviation.
mean of 1st set : 70
mean of second set :0
mean of third set : 40

my answer would be : BCA ...OPTION CHOICE (E)
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 23 Nov 2011, 20:47
Yup..this can be solved just by applying the logic.

In A, when you introduce 100, it falls within the range, so addition of 100 would not deviate much.
In B, when you introduce 100, you are definately deviating from the range and the deviation should be more as you are introducing a large positive number where as the least one is negative.
In C, when you introduce 100, you are also introducing a number outside its range but the deviation will be less as compared to B as all the values are positive.

So depending on range and mean, you can solve this.

So the ans will be BCA....
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 24 Nov 2011, 03:32
you're right, I am sorry, didn't see adding 100 so yes BCA...
I apologize again if I made anyone confused
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 11 Jan 2012, 13:04
Thanks everyone. You guys are of great help.
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 11 Jul 2016, 01:21
vaibhav123 wrote:
manalq8 wrote:
B) ABC
you dont even need to calculate anything
it is easy...the smaller the range between numbers, the smaller the Standard Deviation and vice versa, the larger the difference or the range between numbers the larger the SD

hope this helps


I dont think increase in the standard deviation depends on the range ..

The more is distance of 100 from the mean of each set, the more increase is going to be there in standard deviation.
mean of 1st set : 70
mean of second set :0
mean of third set : 40

my answer would be : BCA ...OPTION CHOICE (E)



when we will add 100 to each set , average of each set will change.

My question is: will the order BCA be same in this case. please clarify
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 13 Oct 2018, 08:22
Standard diviation is square root of average of square of distances from a number to the arimetic means. so, if we add a number which is far from the mean of the set, the new arimetic mean will be far from the old arimetic mean but the distances to the new arimetic mean will be greater than the distances to the old mean.

choice E.
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 14 Oct 2018, 18:15
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Re: Sets A, B and C are shown below. If number 100 is included in each of  [#permalink]

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New post 14 Oct 2018, 21:12
enigma123 wrote:
Sets A, B and C are shown below. If number 100 is included in each of these sets, which of the following represents the correct ordering of the sets in terms of the absolute increase in their standard deviation, from largest to smallest?
A {30, 50, 70, 90, 110}, B {-20, -10, 0, 10, 20}, C {30, 35, 40, 45, 50}
(A) A, C, B
(B) A, B, C
(C) C, A, B
(D) B, A, C
(E) B, C, A

Any idea how to solve these guys please? And what will be the answer? OA is not provided. Also, can GMAT ask to calculate the SD?


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Re: Sets A, B and C are shown below. If number 100 is included in each of   [#permalink] 14 Oct 2018, 21:12
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Sets A, B and C are shown below. If number 100 is included in each of

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