1. Department of Medical Informatics, Biometry and Epidemiology; Friedrich-Alexander University; Erlangen-Nuremberg, Waldstraße 6 91054 Erlangen Germany
2. Department of Medical Biometry, Informatics and Epidemiology; University of Bonn; Sigmund-Freud-Straße 25 53127 Bonn Germany
3. Division of Biostatistics-C060; German Cancer Research Center; Im Neuenheimer Feld 581 69120 Heidelberg Germany