Sam Mason <s...@samason.me.uk> writes: > t = 0.54 ((avg1 - avg2) / (stddev * sqrt(2/samples)))
> We then have to choose how certain we want to be that they're actually > different, 90% is a reasonably easy level to hit (i.e. one part in ten, > with 95% being more commonly quoted). For 20 samples we have 19 degrees > of freedom--giving us a cut-off[1] of 1.328. 0.54 is obviously well > below this allowing us to say that there's no "statistical significance" > between the two samples at a 90% level. Hmm, so what about 95% or 99% confidence? regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers