On 02/18/2015 08:34 PM, David Fetter wrote:
On Tue, Feb 17, 2015 at 08:21:32PM -0500, Peter Eisentraut wrote:
On 1/20/15 6:32 PM, David G Johnston wrote:
In fact, as far as the database knows, the values provided to this
function do represent an entire population and such a correction
would be unnecessary. I guess it boils down to whether "future"
queries are considered part of the population or whether the
population changes upon each query being run and thus we are
calculating the ever-changing population variance.
I think we should be calculating the population variance.
Why population variance and not sample variance? In distributions
where the second moment about the mean exists, it's an unbiased
estimator of the variance. In this, it's different from the
population variance.
Because we're actually measuring the whole population, and not a sample?
cheers
andrew
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
