[Intel-gfx] [PATCH i-g-t 07/18] stats: Add a note about the standard deviation derived from unbiased variance

[Damien Lespiau]

Signed-off-by: Damien Lespiau <damien.lespiau at intel.com>
---
 lib/igt_stats.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/igt_stats.c b/lib/igt_stats.c
index 12cabba..bd05550 100644
--- a/lib/igt_stats.c
+++ b/lib/igt_stats.c
@@ -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.
  *
-- 
2.1.0