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Re: [Phys-l] Significant figures -- again



I wish my students had that natural healthy laziness. Many of my students write every digit from their calculator which most probably indicates that they don't understand uncertainty in measuring. I don't think this is harmless; students need to indicate in their responses that there is a limit to the precision of their answers. I don't take off points for this, but I do comment on it.

Steve Clark

-----Original Message-----
From: John Denker <jsd@av8n.com>
Sent: Mar 8, 2012 10:32 PM
To: Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
Subject: Re: [Phys-l] Significant figures -- again

On 03/08/2012 07:20 PM, Jeff Bigler wrote:
I don't take
off any points as long as they're within about ±2 of what a formal
treatment of sig figs would call for.

I agree with the sentiment, but ±2 isn't where I would draw the
line.
-- As for the lower bound, you almost always want at least one
guard digit, i.e. one more digit than the sig figs rules would
allow.
-- As for the upper bound, you almost never need to worry about
it. Natural healthy laziness limits the number of digits the
students will write down. You might get one wise-guy per year
who writes 43.8574638899607879698958476525252427398409506 ± 3.0
... but even that is harmless.

I insist that nobody is ever required to round anything off.
They are /allowed/ to round off when convenient, provided it
doesn't introduce any unintended loss of accuracy.
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