Re: OT: definition of "significant figures"

[Jacob Sparre Andersen <sparre@nbi.dk>]

Adrian Wrigley wrote:
> On Fri, 29 Jul 2005 16:46:36 +0200, Jacob Sparre Andersen wrote:
> > tmoran@acm.org writes:

> >> Given a set of measurements x(i), I'd like to print their average
> >> to the "correct" number of significant figures.  eg 1.11, 1.12,
> >> 1.08 => "1.1", 1.11, 1.25, 1.35 => "1" I've got some adhocery
> >> that more or less does it, but is there a moderately standard,
> >> formal, definition?
> > 
> > The base 10 logarithm of the standard-deviation of your measurements.
> 
> this looks like one of those physicist's sign errors!

I know. ;)

> How about:
> 
> *Minus* the base 10 logarithms of the standard deviation =>
>   *decimal places*

Yes.  Apparently I didn't even understand the question.

> For example:
> SD=0.1   => use 1 decimal place
> SD=0.001 => use 3 decimal places
> 
> Note that decimal places are not significant figures!

Yes.

> Significant figures = Log10 (mean / standard deviation) + C
> 
> I think people also add in the (small) constant, for good measure,
> depending on how they feel about the data distribution.

Yes.

Jacob (who should start thinking before he posts)
-- 
Growing older is compulsory. Growing up isn't.