Re: [sdpd] error measurements

[cockcroft...@gordon.cryst.bbk.ac.uk]

I agree 100% with Armel about R-factors (and illustrate in particular
about the effect on background subtraction in our PD web course at
Birkbeck). I suspect the output of some programs are not very clear
concerning R-factors (or even weights - since I suspect there are still
many that use unit weights (i.e. non at all!)). I pointed out some
of these problems recently at CDCC, but as I said during my talk,
there will always be those who like to quote R-factors including
background because the numbers are lower, and there will always be
those who quote chi-squared values only becuase they wish to hide the
fact that the data is not of the highest quality.
Just the opinion of another powder crystalllographer,
         Jeremy Karl cockcroft.