Institute for Medical Informatics, Statistics and Epidemiology, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany. vzuber@uni-leipzig.de|Institute for Medical Informatics, Statistics and Epidemiology, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany. vzuber@uni-leipzig.de|Institute for Medical Informatics, Statistics and Epidemiology, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany. vzuber@uni-leipzig.de