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||This article may be too technical for most readers to understand. (September 2010)|
Making notation consistent
I'm going to make some changes late in the article to establish consistent notation. Right now in the section Population variance and sample variance we have in the subsection Sample Variance:
- Taking directly the variance of the sample gives:
- Correcting for this bias yields the unbiased sample variance:
with no definition given for S, though is usually (and subsequently here) notated as s2. Then in Distribution of the sample variance we have an analysis of s2 with no definition having been given for it. Then in Samuelson's inequality we have
- Values must lie within the limits m ± s (n − 1)1/2 .
with m and s undefined (and s meaning something different from previously). Finally, in Relations with the harmonic and arithmetic means we have
- ... where m is the minimum of the sample
in which m means something different from in the previous subsection.
Poisson variance derivation
Right now the Poisson section says:
- The variance is equal to:
- True, and easy to check that the formula given above is false. Also the zero term is missing. Since all terms in the sum are non-negative, and the zero term is positive,
- Formula for binomial variance in same section is also wrong. Mathstat (talk) 20:19, 10 July 2013 (UTC)
Meaning (interpretation) of Variance
While reading the article on variance, I found that a paragraph on how variance should be interpreted (in an intuitive way) was somehow missing. I don't feel confident to write that bit myself, but if someone could add this part it would I believe make the article more interesting and complete. — Preceding unsigned comment added by Marc saint ourens (talk • contribs) 18:29, 1 September 2013 (UTC)
Variance for six-sided die
Isn't the variance given in the article only correct for an infinite number of rolls of a die? For one roll, the variance is zero. For two rolls, a quick calculation suggests the variance is 5/8. Grover cleveland (talk) 16:27, 4 June 2014 (UTC)