There was an informative discussion on this very topic back in Dec 1-2, 2003 if you browse the CCP4BB archives.
Richard Gillilan MacCHESS On Feb 12, 2014, at 6:43 AM, Cai Qixu wrote: Dear all, Does the I/sigmaI in “Table 1” mean for <I>/<sigmaI> or <I/sigmaI> ? Thanks for your answer. Best wishes, Qixu Cai
