On Tue, 17 Jun 2008, Anastassis Perrakis wrote:
been highly correlated with the phase accuracy of the atomic model. In
practice, about 5-10% of the observed diffraction data (chosen at random
from the unique reflections) become sequestered in the test set. The size
of the test set is a compromise between the desire to minimize statistical
fluctuations of the free R value and the need to avoid a deleterious effect
on the atomic model by omission of too much experimental data.
I could not find the full text of the 1992 paper.
If I remember correctly (Tassos, you would have found it in the basement
of the EMBL in Grenoble ;-)) Axel Brunger states in the 1992 article that
500-1000 reflections are sufficient for his purposes of Rfree
calculations.
Tim
