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

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Director
Joined: 10 Feb 2006
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If d is the standard deviation of x, y, and z , what is the [#permalink]  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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Manager
Joined: 02 Aug 2007
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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
Director
Joined: 11 Jun 2007
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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
Manager
Joined: 07 Sep 2007
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because each number is increased by 5 the standard dev would not change.
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