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Bias of Sample Variance


 
The attached .pdf file "Notes on bias correction of sample variance.pdf" is a demonstration of the theory that explains why we divide by "n-1" instead of "n" when calculating sample variance.  The ratio "n/(n-1)" is a correction for bias when calculating the point estimate of the population variance using sample data.  See "Wackerly, Mendenhall, Scheaffer" Sixth Edition page 372.
 
The attached R script enables a demonstration of the presence of bias and bias correction.

Note that a different bias correction is needed for calculating sample standard deviation.  (need to develop further) 

 
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