[Joseph Pehrson wrote:]
>Actually, John... this is interesting because, if I'd known this, I
>probably wouldn't have been quite as "mystified" as I was after
>Graham's original post. The method you outline immediately above
>seems somewhat "averagy" to me... so it would have seemed more
>sensible.

>Here was Graham's original quote from post 24541:

>>Averages are trickier, you do need to consider all intervals then.
>>The most popular is the root mean squared (RMS). So you take the
>>errors in all intervals, square them all, add them together and
>>return the square root.

Right. That'd be the "Root Sum Square", which, as you've surmised,
wouldn't be very "averagy". In fact, I'm not sure what it would be
useful for. I'm sure Graham, and probably all the other people who
responded to your post yesterday, _do_ know the correct definition, but
all had a "brain fart" (which I know a lot about, 'cause I get them all
the time!).

The RMS value will always be less than the largest absolute value which
goes into its calculation (or equal if all input values are the same or
-same). I can see that you were grasping for that in your original
post. So, you have a better math sense than you realized!

JdL