Dear Tipsters,
The formula for sigma, the SD of the population requires N
If we only wish to know s, the SD of the sample, you can still use n.
But if you are trying to estimate sigma from s, you divide by n-1.
Why?
Because dividing by n give a biased estimate.
n-1 corrects for that and gives an unbiased estimate of sigma from s.
Stuart
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Stuart J. McKelvie, Ph.D., Phone: (819)822-9600
Department of Psychology, Extension 2402
Bishop's University, Fax: (819)822-9661
3 Route 108 East,
Lennoxville, e-mail: [EMAIL PROTECTED]
Quebec J1M 1Z7,
Canada.
Bishop's University Psychology Department Web Page:
http://www.ubishops.ca/ccc/div/soc/psy
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