Exp 2 (dTf) pre and post-lab sig fig.

[robert zellmer]

In Chem 1210 you may have discussed how you can average several
numbers and gain sig. fig.  That is correct according to our sig. fig.
rules.  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 when averaging or graphing only 2 or 3 numbers.

Think about an experiment in which you would be plotting your data.
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 averaged out 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),
but even that can be tenuous depending on the size of the numbers.

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 maybe
report 1 extra s.f. in the f.p.  This will certainly not be the case for 
the pre-lab.
Even for the post-lab you are averaging 3 determinations so don't report an
extra s.f.

Dr. Zellmer
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