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

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If d is the standard deviation of x, y, and z , what is the [#permalink] New post 20 Oct 2007, 08:59
If d is the standard deviation of x, y, and z , what is the standard deviation of x + 5, y + 5, z + 5.


d
3d
15d
d+5
d + 15

Ok, what would be the logic that when applied would give me the answer without going through the calculation. I know there is a simple rule that applies. here. Please help
Thanks

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 [#permalink] New post 20 Oct 2007, 09:06
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You are correct, there is a rule here for solving quickly. When a constant is added to or subtracted from each element in the set, then the standard deviation does not change, however std dev will change with division or multiplication.

a. d
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 [#permalink] New post 20 Oct 2007, 09:08
yuefei wrote:
You are correct, there is a rule here for solving quickly. When a constant is added to or subtracted from each element in the set, then the standard deviation does not change, however std dev will change with division or multiplication.

a. d


yup agreed with A) d

since we are adding a constant, the std dev does not change
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 [#permalink] New post 20 Oct 2007, 09:08
the answer is chose A.

because each number is increased by 5 the standard dev would not change.
  [#permalink] 20 Oct 2007, 09:08
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If d is the standard deviation of x, y, and z , what is the

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