References Index Harvey Goldstein is the Professor of Statistical Methods at the Institute of Education, University of London. He was previously Head of the Statistics Section at the National Children's Bureau. He has published widely on survey methodology and the design and analysis of longitudinal studies. Professor Goldstein is a Fellow of the Royal Statistical Society, a Chartered Statistician and an elected Member of the International Statistical Institute. Toby Lewis is the Director of the Centre for Statistics, University of East Anglia and Emeritus Professor of Statistics at the Open University, where he was Professor of Statistics from 1980 to 1986. He was previously Professor of Mathematical Statistics at the University of Hull. Professor Lewis is a Fellow of the Royal Statistical Society, a Chartered Statistician, and an elected Member of the International Statistical Institute.