>Variance is just square of std. dev, no?

     No !   Stdev is divided by count, Variance by (count - 1)

I think the difference really has to do with what you are calculating.
If you want the std. dev./var. of the data THEMSELVES, divide by the
count.  If you want an estimate about the properties of the POPULATION
from which the data were sampled, divide by count-1.  People have
needs for both in different circumstances.

Perhaps there needs to be two versions, or a function argument, to
distinguish the two uses, both of which are legitimate.

Cheers,
Brook

In response to

• Perl Standard Deviation function is wrong ! at 1998-06-05 10:05:18 from Andreas Zeugswetter

Responses

• Re: [HACKERS] Perl Standard Deviation function is wrong ! at 1998-06-06 01:41:07 from Colin Kuskie

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