[phenixbb] significant figures in reporting Rfree

[Pavel Afonine]

>> what is the common practice with respect to how many significant
>> figures should be used for reporting Rfree
> If you look up crystallographic papers, you'll find that people
> routinely report R-values with 3 significant digits, i.e. 23.4% and
> such.  The fourth digit is unreliable - try refining against the same
> dataset with different test set and you'll find that the Rfree varies
> within at least 0.1% (depending on resolution, data quality, etc).

You don't even need to change the test set to see that even the third 
one is not reliable too:
pages 75-77 here:
http://www.phenix-online.org/presentations/latest/pavel_refinement_general.pdf

Pavel.