Re: what good is "percentage error"?

[Leigh Palmer <palmer@sfu.ca>]

> Today I was looking through a commercial high school physics level lab
> manual, and came across the instruction to perform an experiment once
> and then determine the "percentage error" by calculating
>
> (accepted - measured)/accepted * 100%.
>
> Is this quantity even being taught? How can it be used? It seems to me
> that it is useless at best and misleading at worst, and should never
> be used.

I'm with you! I teach them that that particular delusion is a
conceptual error. I discuss "uncertainties" instead of "errors".
An error os a mistake, so far as I am concerned.

Another view is held by John R. Taylor in his excellent book
"An Introduction to Error Analysis - the Study of Uncertainties
in Physical Measurements" (University Science Books). Taylor
uses the terms interchangeably and without distinction, a
practice which I think unnecessary and prone to the sort of
cognitive error that is implicit in the lab manual you cite.

I believe that there is no value in having two terms with
identical meanings in science. Since one of them has a quite
negative vulgar meaning I don't use it, and I discourage my
students from doing so (although I do let them know that there
are others out there, less clever than I, using "error").

Leigh