1. Statistical and Actuarial Sciences, University of Western Ontario, London, Ontario N6A 3K7, Canada; and McMaster Centre for Transfusion Research, McMaster University, Hamilton, Ontario L8S 4L8, Canada
2. Statistical and Actuarial Sciences, University of Western Ontario, London, Ontario N6A 3K7, Canada
3. Mathematics and Statistics, University of Melbourne, Victoria 3010, Australia
4. Statistics, University of Auckland, Auckland 1142, New Zealand