Raul Miller wrote: > On 6/29/07, John Randall <[EMAIL PROTECTED]> wrote:
>> Why? This shows that the method you are using does not produce an >> unbiased estimator of variance, but mine does. > > This terminology "biased" vs. "unbiased" does not appear to be relevant > when talking about population variance. > True, but it does with estimators: an unbiased estimator of a parameter is a statistic whose expected value is that parameter. >> What is a sample which does not represent the population? > > The issue seems to be completeness. > > The "unbiased" estimator traditionally gets used when dealing with > variance for a sample which is not identical to the population. In > other words, if there's any possibility that the distribution of the > sample is different from the distribution of the population, it seems > to be traditional to use the "unbiased estimator" (n/n-1 when determining > RMS deviation rather than the "biased estimator" of 1 when determining > RMS deviation). I don't understand this. A random sample is defined to be a list of independent random variables each with the same distribution as the population. What does "a sample which is not identical to the population" mean? Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
