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Message Posted: Fri, 30 Jan 2004 @ 21:10:44 GMT


     
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Subj:   Re: Standard deviation: STDDEV_POP
 
From:   Victor Sokovin

Rudel,

Not sure I am a math person but I tried to reproduce the formula and I make it as:

STDDEV_POP = SQRT{ [ COUNT(x)SUM(x**2) - (SUM(x))**2 ] / (COUNT(x))**2 }


I checked the formula with the simple population x1=0 and x2=2:

COUNT(x)=2
SUM(x)=2
SUM(x**2)=4


So, STDDEV_POP = SQRT{[2*4 - 2**2] / 2**2} = 1, which seems to be correct.

In this example I get SQRT(7) with both of the formulae you mention, so until somebody finds a counterexample, I will stick with my formula.


Regards,

Victor



     
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