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[Phys-L] Re: infinite sig. figs.



I agree here, I don't even discuss significant figures in my class. I want
them to learn physics, not get bogged down with how to round a final
answer. To me, it's the process over the product that's important. Not the
"accuracy" of the answer. Rounding to one or two decimal places is fine
with me. As long as you solve the (math) problem correctly, you understand
the physics of what's going on.

Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Friday,
September 23, 2005 at 10:04 AM -0500 wrote:
<snip>
all calculations, even those involving "real-world" examples, are to be
carried out to three decimal places
<snip>

Well, I admit to doing this. For my case, to answer Joel, I tell the
students to carry out the calculations entirely in the calculator, or
Excel, or if using paper write down intermediate results to 5
significant digits... and then report the final answer rounded to
3-significant digits.

Why?

(1) I don't want them to waste time worrying about precision and error
analysis on problem sets and exams for which error analysis is not the
point of the problem. If the goal is to learn the physics (or test the
physics knowledge of the student) why throw extra non-physics hurdles in
front of the student?

(2) I don't have to worry about how I give my data. I can write 2 m/s
rather than writing 2.00 m/s. Why throw extra hurdles at myself when I
am writing exams and problem sets?

(3) Three significant digits are generally satisfactory for typical
problems on exams and problem sets. They are many enough to show what
needs shown, and few enough to be convenient.

I suspect the AP folks are thinking the same thing. Don't throw sig-fig
stuff or error analysis baggage on every problem. Just test the
physics.

Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu
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