From: Damon Jansen (dkjansen@yahoo.com)
Date: Wed Oct 04 2000 - 16:08:17 PDT
Message-ID: <20001004230817.14268.qmail@web116.yahoomail.com> Date: Wed, 4 Oct 2000 16:08:17 -0700 (PDT) From: Damon Jansen <dkjansen@yahoo.com> Subject: Re: Sig Figs
I've very much enjoyed the discussion about sig
figs--I've always had trouble teaching them properly.
Art Fortgang suggests teaching it when they come up,
but I've always been so unorganized that I could not
do it justice in the middle of other things.
Something I found very helpful that I did this year
was to use the drawing program in Microsoft Word
(though any basic drawer could work) and make a bunch
of rulers with different levels of precision. (The
units are arbitrary--the length of the unit is just
whatever Microsoft made it). I give the students a
handout that has 4 lines to measure repeated 6 times.
I tell them that they must pretend that the rulers are
rigid (no folding) and that they cannot write on them.
I then hand them the first ruler, which just has
a "0" and a "40" separated by about 20cm. The next
ruler has a "0" a "20" and a "40", but the basic unit
is the same. As they get more precise rulers, their
measurements get more precise. In fact, as we do a
class poll, it is amazing how the "slightly unknown"
digit will always be plus or minus about 2--just the
way they told me it was supposed to in chemistry.
This activity is a great lead-in to the sig fig
rules on adding measured values--we can actually
derive the rule. (I still haven't figured out a way
to make the multiplication/division rule intuitive, so
if you have ideas, let us know.) Another thing this
helps to do is to try to explain the difference
between precision and accuracy--while all of the
rulers are accurate, they vary in their precision.
If anyone would like a copy of the activity, I can
email or regularmail you one. Just send me an email.
dkjansen@yahoo.com
---Damon Jansen
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