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by vivek.kapoor83 » Wed Jan 07, 2009 9:43 am
any takers on this ?
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by DanaJ » Wed Jan 07, 2009 9:51 am
Mean for x, y, z = m
Mean for x+5, y+5, z+5 = [(x+y+z)+15]/3 = m+5
Because the difference between m+5 and either x+5, y+5 or z+5 is the same as the difference between m and x, y or z (eg. m+5-x-5 = m-x), you will have the same standard deviation.
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by amitabhprasad » Wed Jan 07, 2009 9:54 am
SD should be "d" only.
Remember this two rules..

SD(x+c) = SD(x) c--> constant.
SD(x * c) = c*SD(x)
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by vivek.kapoor83 » Wed Jan 07, 2009 11:16 am
gr8 explanation dana
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by nervesofsteel » Wed Jan 07, 2009 11:27 am
amitabhprasad wrote:SD should be "d" only.
Remember this two rules..

SD(x+c) = SD(x) c--> constant.
SD(x * c) = c*SD(x)
Thanks for reminding.. i forgot the multiplication rule..
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by logitech » Wed Jan 07, 2009 4:02 pm
Once again SD questions test your knowledge not your calculation skills.

Standard Deviation is the distance from the average

A B C can be 0 0 and 0 and the average is 0 and the SD is 0 because they are all the same numbers

if you add the same number to all of them

5 5 5 well, this time the average will INCREASE with the SAME number you added to each number

So NUMBER - AVERAGE = WILL BE THE SAME

and as a result SD wont change!
LGTCH
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