Exp 16 pre and post-lab sig fig.

[robert zellmer]

In class you probably discussed how you can average several numbers
and gain sig. fig.  That is correct.  That's why we take lots of
measurements and average them.  However, in practice when dealing
with experimental data including an additional sig. fig. in an average or
from a graph really can't safely be done with only 2 or 3 numbers.

Think about an experiment in which you would be plotting your data (such
as exp 1 from 1210).  The purpose of a best-fit line is to average out the
random error in your data.  If you had only 2 pts the line would go through
both points and wouldn't have show any effect of random errors.  Adding
one more point wouldn't make it much better. Having at least 4 data points
would make it more plausible to gain a sig. fig. (both when averaging and
from a graph).

When you add up your determinations for the f.p. for each trial adding only
three values isn't enough to give confidence in reporting an extra s.f.
If you did five determinations and averaged those I would say you could
probably report 1 extra s.f.

I thought this had been addressed in the "Directions" button in the on-line
data input program.  I guess it isn't for the pre-lab.  Keep this in mind
for the post-lab input as well.

Dr. Zellmer
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