1. York Trials Unit, Department of Health Sciences University of York York YO10 5DD U.K.
2. MRC Biostatistics Unit, Cambridge Institute of Public Health, School of Clinical Medicine University Forvie Site, Robinson Way Cambridge CB2 0SR U.K.
3. MRC Multicentre Otitis Media Study Group, Department of Psychology University of Cambridge Downing Street Cambridge CB2 3EB U.K.