Institute of Medical Biometry and Epidemiology, Philipps-Universität Marburg, Marburg, Germany. volker.steiss@mni.thm.de|Institute of Medical Biometry and Epidemiology, Philipps-Universität Marburg, Marburg, Germany. volker.steiss@mni.thm.de|Institute of Medical Biometry and Epidemiology, Philipps-Universität Marburg, Marburg, Germany. volker.steiss@mni.thm.de|Institute of Medical Biometry and Epidemiology, Philipps-Universität Marburg, Marburg, Germany. volker.steiss@mni.thm.de