IUCr journals

Data merging statistics for assessing whether to omit measured intensities

Acta Cryst. (2013). D69, 1204-1214 (http://doi.org/nsn); 1215-1222 (http://doi.org/nsp)

[Statistics] Comparison of refinement statistics against real and simulated data (Rfree) with data merging statistics (⟨II⟩ and CC1/2), plotted against resolution. For this example the observed data are better than simulated data out to 1.95 Å resolution, where CC1/2 = 0.27 and ⟨II⟩ = 0.9.

These papers highlight again the half-dataset correlation coefficient CC1/2 as a robust statistic for judging whether to include data to a higher resolution or from other crystals. They show that useful information extends beyond the cutoff point suggested by criteria based on Rmerge, which is inappropriate for this purpose. Hard trimming of high-resolution data, omitting useful information, is unlikely to improve the final model, so premature data truncation is a mistake.

P. R. Evans and G. N. Murshudov; K. Diederichs and P. A. Karplus