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Re: Significant figures - a Modest Proposal



Last year the first question on the Friday quiz was calculating by
estimation. It took the entire semester before they were good at it,
but they did stop bringing calculators to the classroom.

joe

On Fri, 27 Aug
1999, JACK L. URETSKY
(C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE, IL 60439 wrote:

Hi all-
Leigh Palmer writes, in part:
***********************************************************
Has anyone got the impression I've had for years that teaching the
topic of significant figures is counterproductive? It really adds
nothing to the sudents' conceptual grasp of Nature, and the students
often think that the topic is important, like Newton's second law. My
inclination has always been to ignore the subject until a really
egregious example occurs (I may even generate one myself in lecture)
and then treat it by pointing out the *uncertainty* in the result,
*not* the "number of significant digits".
********************************
I agree in part. The significant digits topic is related to
the concept of experimental uncertainty - a topic that I think is much
too difficult for an introductory physics lab. I stopped teaching it,
the last time I taught a physics course.
My own solution has been to ban the use of calculators except
for specific instances. Students are required to estimate all numerical
answers and are penalized for evidence of calculator use or for carrying
out long division (or multi-digit arithmetic in general).
The benefit is threefold: emphasis is on concept rather than calculation,
students have an opportunity to get a "feel" for magnitudes, time is saved.
For those on the list who do not wish to be so bold, many of the TI
calculators can be set to show a limited number of digits.
Regards,
Jack


"I scored the next great triumph for science myself,
to wit, how the milk gets into the cow. Both of us
had marveled over that mystery a long time. We had
followed the cows around for years - that is, in the
daytime - but had never caught them drinking fluid of
that color."
Mark Twain, Extract from Eve's
Autobiography