RE: [ai-geostats] Why degree of freedom is n-1

[Harper, Bill]

Reza,   If you are just asking why n-1 in the formula commonly found in stat books for computing the sample variance s^2, it is so that we have an unbiased estimate of the population variance – look at a good calculus based probability and stat book.   Other estimation methods (e.g., maximum likelihood) divide by n instead of n-1.    Oh, while the n-1 does make the sample variance s^2 an unbiased estimate of the population variance sigma^2, taking the square root and getting the sample standard deviation s does not result in an unbiased estimated of the population standard deviation sigma.  Another reason some prefer m.l.e.   Best,   Bill   -- William V Harper, Mathematical Sciences Otterbein College, Towers Hall 139, 1 Otterbein College Westerville OH 43081-2006  USA Office phone: 614-823-1417     Office Fax 614-823-3201 Faculty page: http://www.otterbein.edu/home/fac/WLLVHRPR For the best in geostatistics: http://geoecosse.hypermart.net/   From: Reza Nazarian [mailto:[EMAIL PROTECTED] Sent: Thursday, August 25, 2005 3:23 PM To: ai-geostats@unil.ch Subject: [ai-geostats] Why degree of freedom is n-1   Dear Experts Sorry may be the question is so basic .After searching my statistics books to find an answer with no great success, could you please explain me why we consider degree of freedom as n-1 in calculating variance. Thanks for your kind advises. Very Best Regards Reza Nazarian Schlumberger Information Solutions SONILS Oil Services Centre, Porto de Luanda, Angola (Via UK: +44 (0)207 576 6306 * [EMAIL PROTECTED] http://www.sis.slb.com

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