[1] Univ Glasgow, Glasgow G12 8QQ, Lanark, Scotland
[2] Queen Mary Univ London, London E1 4NS, England
[3] MRC, Biostat Unit, Cambridge CB2 2BW, England
[4] Pfizer Global R&D, Stat Applicat, Sandwich, Kent, England
[5] Quintiles Ltd, Bracknell, Berks, England
[6] Univ Cambridge, Cambridge CB2 1TN, England
[7] Kings Coll London, London WC2R 2LS, England