H_test expl NCI, Macromolecular Crystallography Laboratory, Synchrotron Radiation Research ANL Yates S(H) test data have to be processed in low symmetry H = |I 1 obs – I 2 obs | / (I 1 obs + I 2 obs ) I 1 and I 2 are twin-related cumulative distribution of H is linear S(H) = H / (1 - 2  ) = ½ -  = (1 – 2a) 2 /3 Weak reflections can be discarded
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