(All probabilities with entries '1.0000' in this table and the next actually have values slightly less than one, but nearly equal 1.0000 to four significant decimal places).
For this reason, I have seen curricula vitae in which a scientist annotates each of his or her publications with its journal impact factor listed to three significant decimal places (for example, 11.345).
We wonder why the JIF is calculated to three significant decimal places, but then realize that besides making journals easier to rank, a number calculated to 1/1000 feels somehow more legitimate, more precise – more scientific – than a mere whole number.
In this instance a combination of significant digits and decimal places, the rule of four, 11 works best: round the risk ratio to two significant digits if the leading non-zero digit is four or more, otherwise round to three.
Twenty-nine studies were identified with adequate controls to identify specific effects of homeopathic preparations, reporting significant effects of decimal and centesimal homeopathic potencies, including dilution levels beyond Avogadro's number.
As a third example, p values, it has been suggested, should be rounded to one or two decimal places. 2 For p values above the conventional 0.05 cut-off there is little justification for quoting more than one decimal place, while for significant results three or even four decimals may be necessary.
Published protein coordinate data contain three putatively significant figures after the decimal point, in Angstrom Å units.
*- All p-values rounded to 3 decimal places; nominally significant p-value is in bold.
A number's precision relates to its decimal places or significant figures (or as preferred here, significant digits).
But equally, and perhaps surprisingly, a significant digits rule that ignores decimal places does not always work either.
As in our previous reports (Gulson et al. 1995, 1997a, 1998b), our data are expressed as Pb Pb ratios for ease of identifying and illustrating changes, especially for readers with limited experience in isotopic methods and for whom significant differences in the third decimal place of a ratio of, say 0.900, may seem unrealistic.
