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

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Manager
Joined: 05 Jul 2006
Posts: 198
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Kudos [?]: 20 [0], given: 0

If d is the standard deviation of x, y, and z, what is the [#permalink]  22 Aug 2006, 12:08
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If d is the standard deviation of x, y, and z, what is the standard deviation of x+5, y+5 and z+5?

d
3d
15d
d+5
d+15
Director
Joined: 06 May 2006
Posts: 781
Followers: 3

Kudos [?]: 16 [0], given: 0

Hmmm - I think its A...

The difference of each of the values with their mean does not change, so the SD should not change as well...
Senior Manager
Joined: 14 Jul 2005
Posts: 402
Followers: 1

Kudos [?]: 12 [0], given: 0

d it is ! The answer should be A...

The difference between the mean and the actual numbers will remember the same.
Manager
Joined: 09 Jul 2006
Posts: 85
Location: India
Followers: 1

Kudos [?]: 0 [0], given: 0

mean will change
new mean = (x+5+y+5+z+5)/3 = old mean + 5
but as each of the data points has moved ahead by 5 and even the mean has moved ahead by 5, the SD (which is nothing but a representation of relative distance b/w mean and each of the data points) will remain the same.
this can be shown mathematically as well.
Hence A.
_________________

Cheers!
Prashrash.

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