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If d is the standard deviation x, y, and z, what is the stan

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If d is the standard deviation x, y, and z, what is the stan  [#permalink]

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New post Updated on: 02 Oct 2013, 03:28
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If d is the standard deviation x, y, and z, what is the standard deviation of x + 5, y + 5, z + 5 ?

A. d
B. 3d
C. 15d
D. d + 5
E. d + 15

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-d-is-the-standard-deviation-x-y-and-z-what-is-the-stan-93979.html

Originally posted by gmacvik on 07 Oct 2006, 12:52.
Last edited by Bunuel on 02 Oct 2013, 03:28, edited 1 time in total.
Edited the question and added the OA.
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New post 07 Oct 2006, 14:59
2
If d is the standard deviation x,y,and z, what is the standard deviation of x+5,y+5,z+5

1) d
2) 3d
3) 15d
4) d+5
5) d+15

mean = x+y+z+15 / 3 = x+y+7/3+5

varinace = (mean - each value )^2

mean increased by 5 and each value increased with same value

thus variance remains as is and thus sd is the same
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New post 07 Oct 2006, 15:57
Right - adding or subtracting the same number to all numbers in a set does not change the SD. Multiplying or dividing the same number to all numbers in a set does change the SD.
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New post 08 Oct 2006, 03:15
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Answer is A

Few Tips about SD.

1) If you a add a constant to all terms of a set SD remains the same
2) If you multiply all terms by a constant k new SD k times old SD
3) To determine whether SD for set A is greatero kno SD for a set B we need to the actual terms. Any information abt mean median or range or their combination is not sufficient.
4) basically SD is tedency to deviate from mean. More data deviates more is sd and less the data smaller is SD.

HTH
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New post 08 Oct 2006, 05:11
D)d+5

Pure POE and guess work - so, if not D, then it's A.
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New post 08 Oct 2006, 06:07
It is A.

Hey Yogesh, that's what the aspirants here need................
Keep rocking.........
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Re: If d is the standard deviation x, y, and z, what is the stan  [#permalink]

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New post 02 Oct 2013, 03:30
5
12
If d is the standard deviation x, y, and z, what is the standard deviation of x+5, y+5, z+5

A. d
B. 3d
C. 15d
D. d+5
E. d+15

TIP:
If we add or subtract a constant to each term in a set:
Mean will increase or decrease by the same constant.
SD will not change.

If we increase or decrease each term in a set by the same percent (multiply by a constant):
Mean will increase or decrease by the same percent.
SD will increase or decrease by the same percent.

So in our case SD won't change as we are adding 5 to each term in a set --> SD=d.

Answer: A.

More about standard deviation:
math-standard-deviation-87905.html
ds-questions-about-standard-deviation-85896.html
ps-questions-about-standard-deviation-85897.html

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-d-is-the-standard-deviation-x-y-and-z-what-is-the-stan-93979.html
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Re: If d is the standard deviation x, y, and z, what is the stan  [#permalink]

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New post 30 Jul 2018, 14:04
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Re: If d is the standard deviation x, y, and z, what is the stan &nbs [#permalink] 30 Jul 2018, 14:04
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