Correct me if I'm wrong, but at least initially, the first listed goal of statistics (per the PEP) was:

"Correctness over speed. It is easier to speed up a correct but slow function than to correct a fast but buggy one."

numpy already exists for people who need insane speed for these algorithms and are willing to compromise accuracy; am I wrong in my impression that statistics is more about providing correct batteries included that are fast enough for simple uses, not reimplementing numpy piece by piece for hardcore number crunching?

Even if such a function were desirable, I don't like the naming symmetry between fsum and fmean; it's kind of misleading. math.fsum is a slower, but more precise, version of the built-in sum. Having statistics.fmean be a faster, less accurate, version of statistics.mean reverses that relationship between the f-prefixed and non-f-prefixed versions of a function.