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Date: Sun, 26 Sep 2004 18:58:27 -0400
From: Phil Steitz <phil@steitz.com>
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To: Jakarta Commons Developers List <commons-dev@jakarta.apache.org>
Subject: Re: [math] API changes for RC2
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 <41576D45.7080003@kimvdlinde.com>
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Kim van der Linde wrote:
> 
> 
> Al Chou wrote:
> 
>> -0; question:  do people really use the population version?  When 
>> dealing with
>> real-world data or any other distribution that is not known a priori, 
>> how could
>> you, in good conscience?  And if you know the distribution a priori, 
>> why would
>> you need to compute statistics about it?
> 
> 
> It depends if you want to minimise error or bias. 

This is a good point. Strike the "haughty" assertion in my last post -- 
i.e. it is not always "bogus" in practical terms to use a biased estimator.

> We do use it at times, 
> just like we do change degrees-of-freedom (in many of our multivariate 
> analyses by 4 to be precise due to three modifications that take 1, 1, 
> and 2 degrees of freedom) in all kind of tests to correct for previous 
> calculations on the same data set. In some studies, the variance is 
> calculated relative to a set average, which become biased 
> the-other-way-around if you would use sample variances.

Yes, this was the first case that I mentioned.
> 
> Anyway, I reported these examples back because of the real life usage.
> 
> Cheers,
> 
> Kim
> 


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