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Message Posted: Fri, 27 Feb 2004 @ 11:59:10 GMT


     
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Subj:   Re: Standard Deviation formula
 
From:   Mansfield, John

Hi

The STDDEV_POP equation is equivalent to your SD equation. The key difference between the two being the denominator of N in the pop version versus (N-1) in the samp version.

This can be demonstarated by expanding the term in the sum, but I leave that to you to do if you want.

This method is however subject some rounding error, but allows the computation in one pass through the data. This is most noticeable if the values are different by orders of magnitude.



     
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