standard deviation

[Jack L. Vevea]

In article <9847 at ihlpl.ATT.COM> kat3 at ihlpl.UUCP (Craig,R.J.) writes:
>------------------------- cut here -------------------------
>The input data is given below:
>------------------------- cut here -------------------------
>10
>111111111.0
>111111112.0
>111111111.0
>111111112.0
>111111111.0
>111111112.0
>111111111.0
>111111112.0
>111111111.0
>111111112.0
>-------------------------- cut here ------------------------
>
>
>Notice that the onepass standard deviation is 1.78, while the twopass
>standard deviation is 0.5!!!!!!  Incidentally, the true value is 0.5!!
>


	Sure; and you could just as easily have picked another data
set that produced a correct result from the onepass program, and an
incorrect result from twopass.  Which is why, as has been pointed out
before, neither algorithm should be used in a general standard
deviation program.

	There was a posting recently to sci.math.stat, not crossposted
here, that gave a reference for better computational algorithms.








Saepe fidelis.