✦ LIBER ✦

Separating model optimization and model validation in statistical cross-validation as applied to crystallography

✍ Scribed by Kleywegt, Gerard J.

Publisher: International Union of Crystallography
Year: 2007
Tongue: English
Weight: 127 KB
Volume: 63
Category: Article
ISSN: 0907-4449
DOI: 10.1107/s0907444907033458

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✦ Synopsis

Statistical cross-validation has become an integral part of the model-refinement process in macromolecular crystallography. However, the test set of reflections, for which the free R value is calculated, is used both to optimize the parameterization of the structure model and to validate the model itself. This practice could introduce bias and diminish the value of R free as an independent check of model quality. It is proposed here that by introducing a dormant holdout set of reflections, any problems with such bias can be avoided. This procedure requires only a small modification of the standard cross-validation protocol.

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