Institution: | 1. I‐BioStat, Universiteit Hasselt, B‐3590 Diepenbeek, Belgium;2. Epidemiology and Social Medicine, Universiteit Antwerpen, B‐2610 Antwerpen, Belgium;3. I‐BioStat, Katholieke Universiteit Leuven, B‐3000 Leuven, Belgium;4. Medical Statistics Unit, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK |