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Re: [Phys-l] Significant figures -- again



On 03/13/2012 01:52 PM, Richard Tarara wrote:
I would also be against the three-decimal place rule you suggest.

What I actually said was

round everything off to 3 decimal places (in
scientific notation) and leave it at that. (Worrying about
the uncertainty can come later, if at all.)

Additional details can be found at
http://www.av8n.com/physics/uncertainty.htm#sec-postpone-uncertainty

For
example, we do some simple Ohm's law labs using VI graphs to get the
resistances of some 'black boxes', individually and in series and parallel.
The digital voltmeter reads to a 100th of a volt and we use a 0-10 volt
range and the analog ammeters can be read to no better than 3 digits. Now
we go to EXCEL for graphing and fitting. Typically the resistances are in
the 50-200 ohm range. I really don't see that letting students report that
the resistance was 125.264 Volts/Amp is reasonable. I really want 125 or at
worst 125.3 as the reported value. Sig Figs handles this.

Three digits of scientific notation handles this just fine,
with less effort for everybody, and less nonsense that will
have to be unlearned later.

====

I pretty much agree with everything Robert Cohen wrote on 03/13/2012 01:59 PM,
including the all-too-typical example of the perils of rounding off intermediate
results.