Stephen L R Ellison is head of the Bioinformatics and Statistics team at LGC. His current research interests include the characterisation of uncertainties arising from analytical recovery and matrix effects. An author of the EURACHEM guide 'Quantifying Uncertainty in Analytical Measurement', Dr Ellison is a recognised international expert in measurement uncertainty principles applied to analytical methods. He contributes to a range of national and international committees in that field. Vicki J Barwick is currently project manager at LGC for the Chemical and Biological Metrology programme knowledge transfer projects (funded by the National Measurement Office). These are aimed at promoting the adoption of the principles of valid analytical measurement. Over the last 10 years, she has lectured extensively on quality assurance topics and has co-authored a number of papers, books and guides. Trevor has recently joined Cadbury as the Global Statistics Program Leader. Here his team work with sensory data from trained panels and consumers. They analyse all chocolate, gum & candy to ensure production & development of the world's best confectionery. Prior to that he worked 10 years at Gillette (P&G) coordinating their statistical capabilities. He and his team developed a wide range of techniques to analyse quality control, expert panel, consumer and analytical data. He is the recognised expert in shave test methodology and is responsible for many novel applications of statistical theory. Before Gillette he spent 10 years at LGC as the Chemometrics & Statistics Manager, where he wrote the first edition of this book. As the former chairman of the Business & Industry section of the Royal Statistical Society he has broad statistical interests. His current research includes compressed space experimental design and neutral versus forced choice preference questions.