Department of Medical Informatics, Biometry and Epidemiology, University of Munich, Marchioninistr 15, D-81377 Munich, Germany. boulesteix@ibe.med.uni-muenchen.de|Department of Medical Informatics, Biometry and Epidemiology, University of Munich, Marchioninistr 15, D-81377 Munich, Germany. boulesteix@ibe.med.uni-muenchen.de