Roger Hui wrote: > The description in textbooks is that sd2 is "more efficient" > (fewer operations) than sd. Said textbooks were > written in the days when desk calculators were used > to compute the things.
Having learned back in those days, the fewer operations message may have stuck. I still think there is a problem if a lot of values are close to the mean, since calculating the difference will cause loss of precision, but the justification I had was false. Standard deviations are used in a way that does not require much accuracy, so it may not matter anyway. Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
