F-test in EXAFS fitting of structural models

The principles of the statistical F-test, used in EXAFS fitting in order to compare different models and eventually choose the more likely, are summarized. Examples, taken in the fields of inorganic chemistry and biochemical applications are discussed. F-test is shown to be very useful to check the statistical limits of a model and to discriminate between physically acceptable models. However, this tool is useless when the choice involves physically unrealistic solutions since it cannot prevent parameter variations out of their physically significant limits.