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From: "saneman" <asd@ad.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Variance?
Date: Thu, 15 May 2008 23:38:36 +0200
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"Roger Stafford" <ellieandrogerxyzzy@mindspring.com.invalid> skrev i en 
meddelelse news:g0i9li$qum$1@fred.mathworks.com...
> "saneman" <asd@ad.com> wrote in message <g0i78i$ltc$1@news.net.uni-
> c.dk>...
>> I have a vector that contains:
>>
>> v = 0.5677    0.4792    0.4844    0.4870    0.5104    0.4870    0.4792
>> 0.4974    0.4688    0.4870
>>
>> Now I would like to know how much this data varies. I was thinking:
>>
>> a = max(v) - min(v)
>>
>> But if just one sample is very different (like 10.0) then the above
>> procedure will not give a realistic result.
>>
>> I have also tried to use the matlab var function:
>>
>> >> var(v)
>>
>> ans =
>>
>>   7.7977e-004
>>
>> But 0.0007 is not where most of the data belongs. Is there better 
>> approach
>> to this problem?
> ------------
>  Remember, the 'var' function returns the mean of the *squares* of the
> differences between your numbers and their mean value.  Your differences
> from their mean are somewhere in the neighborhood of .03 so the mean
> square of these differences would be in the neighborhood of .0009. 
> (Actually
> you got .0008 .)  To get a value which is comparable to these differences, 
> you
> should either call on 'std' or take the square root of the variance.
>

How is it possible to use these functions on the data without supplying 
information about the probabilities?