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



Veryt nice! The moral is, I thinkk, it's not enought to ask the right question, but you must as it, using the right words.
Nice thought.
Regards,
Jack

"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley




On Mon, 12 Mar 2012, Paul Lulai wrote:

I've found that stating in terms of what they can measure or make helps a bit. When a kid gives me an answer of 3.8675309 cm (or anythings), I ask them if they could cut a board to that length. It seems that they are less comfortable making something a certain length (or weight etc...) than they are measuring to that precision. Meaning if you give a 9th grader (or 12th grader, and I assume college kid) a board to measure, they are happy to claim it is 3.8675309 cm long. Asking them to cut a board to that length makes them think a bit more about what is appropriate.

Paul Lulai
Physics Teacher
St Anthony Village S.H.
3303 33rd Ave NE
St Anthony Village, MN 55418

612-706-1146
plulai@stanthony.k12.mn.us
http://www.stanthony.k12.mn.us/hsscience/ ;


-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Richard L. Bowman
Sent: Saturday, March 10, 2012 3:13 PM
To: sclarkphd@mindspring.com; Forum for Physics Educators
Subject: Re: [Phys-l] Significant figures -- again

Steve,

My experience with college students, even with science majors but especially with non-science majors, is the same as yours. And this is why I do teach significant figures to make them conscious of uncertainty in all of the data they see in life, from lab measurements to results of political surveys. And I do take off points for not applying the concept, but I do give them the latitude of +/- digit which I know does not make sense in a technical sense, but for my pedagogical purposes (in general education at the college level), I think it makes a lot of sense.

Richard

Richard L. Bowman, PhD | Department of Physics | Professor of Physics BRIDGEWATER COLLEGE, Bridgewater, VA 22812, USA
phone: 540-828-5441 | online: www.bridgewater.edu/~rbowman ________________________________________
From: phys-l-bounces@carnot.physics.buffalo.edu [phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of sclarkphd@mindspring.com [sclarkphd@mindspring.com]
Sent: Friday, March 09, 2012 9:56 PM
To: Forum for Physics Educators
Subject: 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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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
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Forum for Physics Educators
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