1. Center for Medical Biometry and Medical Informatics Medical Center – University of Freiburg
2. Department of Epidemiology and Biostatistics McGill University Montréal, QC H3A 0G4 Canada
3. Centre for Statistics in Medicine University of Oxford Oxford OX3 7LD [Correction added on 15 August 2014, after first online publication: Postcode OX1 2JD has been corrected to OX3 7LD] U.K.
4. Department of Clinical Epidemiology and Department for Medical Statistics and Bioinformatics Leiden University Medical Centre 2333 ZA Leiden The Netherlands
5. Medical Statistics Unit London School of Hygiene and Tropical Medicine, and MRC Clinical Trials Unit Kingsway London U.K.