On Sat, 23 Mar 2002 01:45:27 +0100, "ParkStein" <[EMAIL PROTECTED]> wrote: >why root (sigma (average - x(i))^2) ? >why not sigma |average - x(i)| ?
I think you should be dividing by n in both of these, but in answer to your question, you can choose from the following simplified choices: a) the standard deviation is a simple function of the variance b) it is easy to calculate the standard deviation of the sum of two independent random variables if you know their standard deviations c) it means taking greater account of points further away d) it partners the mean, while the average deviation partners the median d) |x| is not differentiable at 0 . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
