作者单位:Independent Biostatist Consultant, Levittown, PA USA[1]Cytel, Strateg Accounts, Cambridge, MA USA[2]Roche, Biostat, Welwyn Garden City, Herts, England[3]Cytel, Consulting Dept, Cambridge, MA USA[4]ICON Plc, Innovat Ctr, Cologne, Germany[5]Amgen Inc, Ctr Design & Anal, Thousand Oaks, CA 91320 USA[6]AbbVie Inc, Data & Stat Sci, N Chicago, IL USA[7]Eli Lilly & Co, Global Stat Sci, Indianapolis, IN 46285 USA[8]