Talk:Standard deviation

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Incorrect diagram under section "Interpretation and application" ?[edit]

The red and blue populations are supposed to have mean = 100 but from inspection the red one clearly appears to have a lower mean.

Those are samples from the populations, not the populations themselves. Dghu123 (talk) 16:26, 31 December 2016 (UTC)

Please use proper colors in the drawings[edit]

The chosen colors are like a color vision test. Please use distinct and bright colors, especially because of green, yellow and red being too close. It's more important to be accessible than to pick colors by other factors. Bright yellow, bright green and red, make it more accessible. Thanks. I am referring to this picture in particular: Variance_visualisation.svg

Contradiction between Wikipedia pages?[edit]

There seems to be a direct contradiction between a statement in this article (in section "Basic Examples"):

Dividing by n − 1 rather than by n gives an unbiased estimate of the standard deviation of the larger parent population. This is known as Bessel's correction.[5]


And the article referenced on Bessel's correction (in section "Caveats").

There are three caveats to consider regarding Bessel's correction:

It does not yield an unbiased estimator of standard deviation.

Vector Shift (talk) 03:27, 14 March 2017 (UTC)


Also could someone explain the blue background areas and why the boldface I tried to use in the second quote works differently in the blue background area and the other part of the quote that for some reason, isn't in the blue background area?

Vector Shift (talk) 03:27, 14 March 2017 (UTC)

Bessel's correction gives an unbiased estimator of the variance, but not of the square root of the variance, i.e. the standard deviation.
The formatting didn't work the way you wanted as Mediawiki interprets a space at the beginning of a line of wikisource as requesting monospace font and a grey background. This is designed for quoting code - personally I think it's a misfeature. I've taken the start-of-line spaces out of your input above and replaced by colons, which is wiki syntax for indenting. Qwfp (talk) 06:48, 14 March 2017 (UTC)

geometric visualization[edit]

I don't get the "geometric visualization" image. I mean, I understand how it works and see that it is correct, but I don't understand how it is supposed to help anyone understand what variance is. The last step is just a sort of algebraic trick, and I find it mathematically uncomfortable because it converts the quadratic-type object variance into the linear-type object distance. Is it just me? McKay (talk) 05:07, 17 March 2017 (UTC)

I agree (i.e it's not just you). Qwfp (talk) 07:31, 17 March 2017 (UTC)
I've now removed the image. Qwfp (talk) 19:30, 17 March 2017 (UTC)