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from Veritas ProjectGMAT. One of their tips with no example

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CEO
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from Veritas ProjectGMAT. One of their tips with no example [#permalink] New post 15 May 2007, 18:45
from Veritas ProjectGMAT. One of their tips with no example shown...

"Adding or subtracting a constant from each element in the set has no effect on the standard deviation"

Can someone elaborate on this?
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Re: standard deviation [#permalink] New post 15 May 2007, 18:52
bmwhype2 wrote:
from Veritas ProjectGMAT. One of their tips with no example shown...

"Adding or subtracting a constant from each element in the set has no effect on the standard deviation"

Can someone elaborate on this?



suppose the value of x are: 10, 11, 13, 15, and 20
now you deduct 5 from each, then x values are: 5, 6, 8, 10 and 15
now you add 5 on each, then values of x are: 15, 16, 18, 20 and 25

the sd is 3.96 in all cases.
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 [#permalink] New post 15 May 2007, 18:53
nevermind. figured it out...


set a (1,2,3,4,5,) Standard deviation of 1
set b (5,6,7,8,9) all terms n+5 . standard deviation of 1

therefore, sd is the same.
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 [#permalink] New post 15 May 2007, 21:26
This happens coz if we subtract or add some constant number from a set of numbers then the average also decreases or increases respectively by same figure thus keeping the difference of numbers and average constant.
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 [#permalink] New post 15 May 2007, 21:37
apache wrote:
This happens coz if we subtract or add some constant number from a set of numbers then the average also decreases or increases respectively by same figure thus keeping the difference of numbers and average constant.


yea. just shifting the entire set (all the elements) by the same ratio or amount.
  [#permalink] 15 May 2007, 21:37
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from Veritas ProjectGMAT. One of their tips with no example

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