1 Centre for Statistics in Medicine, Botnar Research Centre, University of Oxford, Windmill Road, Oxford OX3 7LD, United Kingdom. Electronic address: [email protected].
2 Department of Anesthesia & Clinical Epidemiology, Michael DeGroote School of Medicine, Faculty of Health Sciences, McMaster University, Perioperative Research Group, Population Health Research Institute, Hamilton, Canada; Department of Biostatistics, Michael DeGroote School of Medicine, Faculty of Health Sciences, McMaster University, Perioperative Research Group, Population Health Research Institute, Hamilton, Canada. Electronic address: [email protected].