stats: Add a note about the standard deviation derived from unbiased variance

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
This commit is contained in:
Damien Lespiau 2015-06-26 18:19:42 +01:00
parent da123adeae
commit 17ed69fbb8

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@ -121,6 +121,11 @@ bool igt_stats_is_population(igt_stats_t *stats)
* [Bessel's correction](https://en.wikipedia.org/wiki/Bessel%27s_correction)
* to the variance.
*
* Note that even if we manage to have an unbiased variance by multiplying
* a sample variance by the Bessel's correction, n/(n - 1), the standard
* deviation derived from the unbiased variance isn't itself unbiased.
* Statisticians talk about a "corrected" standard deviation.
*
* When giving #true to this function, the data set in @stats is considered a
* full population. It's considered a sample of a bigger population otherwise.
*