On Wed, Apr 09, 2014 at 08:20:42AM +0000, Wolfgang Maier wrote:
> I do not think this is a bug in the module, but rather incorrect usage.
[...]

No, it is legitimate usage. See, for example, "Numerical Recipes in 
Pascal" by Press et al. When you know the population mean independently 
from the sample you're using, you should not apply Bessel's Correction 
(that is, you should use a denominator of n rather than n-1, which 
is equivalent to using the population variance).

I don't think it is appropriate to include too much of the complexity 
about variance in the docs. (They should document the module, not teach 
all the odd corners of statistics theory.) I've tried to clarify the 
different uses of (p)variance here: 
http://import-that.dreamwidth.org/2291.html

If you're still not convinced, this usage is equivalent to the 
gsl_stats_variance_with_fixed_mean function from the GNU Scientific 
Library:
https://www.gnu.org/software/gsl/manual/html_node/Mean-and-standard-deviation-and-variance.html