From: Art Fortgang (afortga@yahoo.com)
Date: Fri Sep 29 2000 - 01:52:46 PDT
Message-ID: <20000929085246.18649.qmail@web4307.mail.yahoo.com> Date: Fri, 29 Sep 2000 01:52:46 -0700 (PDT) From: Art Fortgang <afortga@yahoo.com> Subject: Sig Figs
I appreciate what is being said about sig figs and the
angst it may cause teachers and students when first
encountering the issue. During the past five or so
years I have withdrawn the issue as a beginning of the
year topic and placed it when arises in class.
For example, averaging 2 and 3 grams. If the balance
measures only to the nearest whole gram the question
becomes how accurate are those measures? Although, 3
grams average sounds ludicrous to a math student, it
shouldn't disturb the science student. Why? When a
math student averages 2 and 3 she finds that 2.5 is
the correct answer. The assumption here is that 2 and
3 are exact numbers. When a science student averages
2 and 3 grams and finds the correct answer is 3 grams
there should be no problem because 2 and 3 grams (as
are all measurements) are not exact and hence the
average is not, nor should it be, exact either.
When students have experiences recording data
(correctly) they ought to be sensitized to writing and
reading data that they know is not exact, and
afterwards the rules of precision and accuracy start
to follow. Again, my experiences are that this works
better (and more efficiently, to boot) when done after
data recording has occurred and not in the beginning
of the year where it is often placed because it is in
the first chapter of most text.
Cheers
--- Pinhole Listserv <pinhole@exploratorium.edu>
wrote:
> Pinhole Digest #473 - Friday, September 29, 2000
>
> Re: pinhole science fair ideas
> by "The Lahrs" <johnjan@lahr.org>
> Re: pinhole vector toy
> by "Deborah Hunt"
> <dhunt@exploratorium.edu>
> Re: pinhole science fair ideas
> by "Deborah Hunt"
> <dhunt@exploratorium.edu>
> Sig figs & averaging
> by "Geoff Ruth"
> <gruth@uclink4.berkeley.edu>
> Re: pinhole Sig figs & averaging
> by "Gary Horne" <gary.horne@excite.com>
>
>
>
----------------------------------------------------------------------
>
> Subject: Re: pinhole science fair ideas
> From: "The Lahrs" <johnjan@lahr.org>
> Date: Thu, 28 Sep 2000 06:56:31 -0600
>
> Heidi,
> There are a range of possible science project ideas
> here:
> http://lahr.org/john-jan/science.html
> Cheers,
> John
> John C. Lahr
> 1925 Foothills Road
> Golden, CO 80402
> (303) 215-9913
> john@lahr.org
> http://lahr.org/john-jan/science.html
>
>
----------------------------------------------------------------------
>
> Subject: Re: pinhole vector toy
> From: "Deborah Hunt" <dhunt@exploratorium.edu>
> Date: Thu, 28 Sep 2000 08:59:15 -0700 (PDT)
>
> These toys are also known as ramp walkers. There's a
> web site called
> JD's Plastic Ramp Walkers where you can get more
> information about them
> and buy them. It's at
> http://www.angelfire.com/mi/rampwalkers/ You
> could also ask at toy stores for ramp walkers.
>
> Deb
>
>
> On Wed, 27 Sep 2000, Black, Heidi wrote:
>
> > AH! My vector toy source went away! I have
> gotten them from Laurel's
> > Wonders and Whimsies on Chestnut-but they are
> gone!!!!
> >
> > Any leads? I'd desparate! I still get requests
> from the vector toy
> > snackbook activity. I have found some similar
> toys in a shop in Los Gatos,
> > but they are designed to "waddle" as they have a
> point that drags, and the
> > string attachment is too low for possibly
> measuring angles.
> >
> > Thanks,
> > Heidi
> >
>
>
> ---------------------------------------------------
> Deborah Hunt
> Internet Resource Specialist
> Exploratorium
> 3601 Lyon Street
> San Francisco, CA 94123
> Voice: 415-353-0485
> Fax: 415-561-0370
> email: dhunt@exploratorium.edu
>
>
>
----------------------------------------------------------------------
>
> Subject: Re: pinhole science fair ideas
> From: "Deborah Hunt" <dhunt@exploratorium.edu>
> Date: Thu, 28 Sep 2000 09:12:57 -0700 (PDT)
>
> We get literally hundreds of emails asking for
> science fair help.
> Our Learning Studio staff have put together an
> awesome resources at:
>
http://www.exploratorium.edu/ls/pathfinders/scifairs/
>
> Deb
>
> ---------------------------------------------------
> Deborah Hunt
> Internet Resource Specialist
> Exploratorium
> 3601 Lyon Street
> San Francisco, CA 94123
> Voice: 415-353-0485
> Fax: 415-561-0370
> email: dhunt@exploratorium.edu
>
>
>
----------------------------------------------------------------------
>
> Subject: Sig figs & averaging
> From: "Geoff Ruth" <gruth@uclink4.berkeley.edu>
> Date: Thu, 28 Sep 2000 13:26:45 -0800
>
> I've been thinking about significant figures a lot
> recently, and
> contemplating when scientists do and don't use them.
> Here's a simple
> example.
>
> If you had two objects with masses of 2 g and 3 g,
> and you wanted to find
> their average, I think that most chemists would
> report the average mass as
> 2.5 g. But according to sig fig rules, their average
> mass should be 3 g.
> That seems slightly insane to me: the idea of
> averaging 2 g and 3 g to get
> 3 g is very weird to me, as well as my students.
>
> Advice?
>
> -Geoff Ruth
> Leadership High School
> 300 Seneca Avenue
> San Francisco, CA 94112
>
>
----------------------------------------------------------------------
>
> Subject: Re: pinhole Sig figs & averaging
> From: "Gary Horne" <gary.horne@excite.com>
> Date: Thu, 28 Sep 2000 13:53:38 -0700 (PDT)
>
> My understanding of significant figures is that the
> last digit is the
> "unsure" value. If I measure a weight that is 23 g,
> then it could be 24 or
> 22 or maybe even 20 grams. I'm sure of the tens
> place, but the one's case
> is "unsure". In your example, the weights may
> measure as 2 and 3 grams, but
> both are unsure measurements. In that light, the
> average of two items that
> are about 3 grams equaling about 3 grams is correct.
>
> If, however, one is sure that the weight is about 2
> grams, she should write
> 2.0 with the tenths place being the "unsure" value.
> Likewise with 3.0. In
> that case, the average is 2.5, and again, makes
> sense.
>
> At least, that is my understanding, but I admit that
> significant figures
> gave this non-chemist a lot of trouble as well.
>
> -gary
>
> On Thu, 28 Sep 2000 13:26:45 -0800, Pinhole Listserv
> wrote:
>
> > I've been thinking about significant figures a
> lot recently, and
> > contemplating when scientists do and don't use
> them. Here's a simple
> > example.
> >
> > If you had two objects with masses of 2 g and 3
> g, and you wanted to find
> > their average, I think that most chemists would
> report the average mass
> as
> > 2.5 g. But according to sig fig rules, their
> average mass should be 3 g.
> > That seems slightly insane to me: the idea of
> averaging 2 g and 3 g to
> get
> > 3 g is very weird to me, as well as my students.
> >
> > Advice?
> >
> > -Geoff Ruth
> > Leadership High School
> > 300 Seneca Avenue
> > San Francisco, CA 94112
> >
> >
>
---------------------------------------------------------------------------
> >
>
=== message truncated ===
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