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

[Paul Lulai <plulai@stanthony.k12.mn.us>]

Brian,
We actually do that at the beginning of the year to convey the uncertainty in a student's measure of length, mass, and volume (from a graduated cylinder). Each student measures a standard objects length, mass, liquid's volume.  Find the average, find the range of reasonable values (this is where I am likely liable by not using st dev).  The value from the average to the largest reasonable value is our uncertainty.
I tell them there are other ways to do it.  This is how we will acknowledge uncertainty exists.

Have a good one.

Paul Lulai (where I've managed to live through a pillory or 2, gotten a bit thicker skin (or a longer neck), and actually have 5 physics majors in college right now (grad h.s. class of ~150) ;)

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 brian whatcott
Sent: Tuesday, March 13, 2012 11:50 AM
To: phys-l@carnot.physics.buffalo.edu
Subject: Re: [Phys-l] Significant figures -- again

On 3/12/2012 9:33 PM, Bernard Cleyet wrote:
> On 2012, Mar 12, , at 19:12, John Denker wrote:
>
> > If I want to read about roundoff errors, I'm not going to rely on 
> > some high-school physics text written by a highly skilled cartoonist.
> > I have other books, including books with "Numerical Methods" in the 
> > title.  I also have my own quantitative observations to draw on.
>
> John, I think you unnecessarily pillory Paul.  I suspect he's caused many students to become physics majors and others to think physically. However, if you've tried to have him correct his texts' errors, and failed that's another matter.
Hmmmm....it seems to me the question of who should pillory whom is quite open.
The suggestion that when a student offers a length to numerous decimal places - far beyond the capability of any tool she has in hand - that this be taken to represent a sample mean is quite ludicrous. Paul could labor the point I suppose, by having a student or several students take numerous measurements of the object  in order to produce something that could more rightfully be called a distribution of the samples, so that the initially offered 2.345678 turns out to have a mean closer to 2.5, but life is short, and the curriculum is long.


Brian Whatcott
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l