On 2016-06-18, Steven D'Aprano <st...@pearwood.info> wrote: > On Sat, 18 Jun 2016 09:49 am, Ian Kelly wrote: > >> If I tell you that the speed of light is 300,000,000 m/s, do you think >> that measurement has 9 significant digits? If you do, then you would be >> wrong. > What if the figure to nine significant digits *actually is* three followed > by eight zeroes?
The you can either write it as 300000000. (notice the trailing decimal indicating that all of the zeros are indeed significant) or write it it scientific notation. > For all that it is in widespread use, I think the concept of "significant > figures" is inherently ambiguous. Only for those who do not understand it. The main problem I have with significant figures is that measurement accuracy is often not constrained to a decimal system. A scale that can measure in 1/5 units is more accurate than a scale that can measure only in whole units but it is not as accurate as a scale that can measure all 1/10 units. Therefore it effectively has a fractional number of significant figures. I could just cut my loses and express the lower number of significant figures but, I usually express the error explicitly instead: <measurement> +- 0.2 units where +- looks like the ± html entity. -- https://mail.python.org/mailman/listinfo/python-list