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[Phys-L] Re: fall cleanup: sig figs



John,

An interesting read. I agree with most of your points about the foll=
y of "sig figs", but I have a few comments.

1) Excel DOES have a way to generate random normal data: Tools; Data=
Analysis; Random Number Generation will generate a half dozen differ=
ent distributions, including normal. You may have to go to Tools; Ad=
d-Ins and install the correct tools.

That said, I have heard that this isn't a very good normal distributi=
on generator for serious Monte Carlo work.


2) You seem to be assuming that all the errors in your analysis are r=
andom, rather than systematic. I had a set of plastic meter sticks t=
hat were consistently 1 mm different in length from a set of wooden m=
eter sticks. I have no idea which was closer to correct, but no amou=
nt of averaging of reading will help make the answer any more accurat=
e when the instrument itself is flawed.

Probably obvious, but often the obvious things are worth saying.


3) You give an example of measuring an object to the nearest 1/4 mm =
by interpolation. Such operations tend to be highly subjective. In =
this case, the operator could have a much larger impact on the result=
than any difference caused rounding and/or sig figs. There is a met=
hodology common in industrial settings known as "Gage Repeatability &=
Reproducibility" ("Gage R&R", or sometimes "Gauge R&R") that explore=
s just such issues.


4) I don't see any mention of accuracy vs precision. In some of you=
r discussion, I think you are more properly interested in precision t=
han accuracy.


Just my $0.02. (How many sig figs is that? ;-) =20

Tim F