The increased awareness of the impact of health care on the quality of human life means that clinical researchers working in a wide spectrum of disciplines need information about soft measures such as pain, depression, or function. A sound, scientific, and reproducible system of measurement is required by clinicians and researchers in disciplines such as psychiatry, rheumatology, oncology and other health professions such as nursing, physiotherapy and occupational therapy. Based on a graduate course developed by the authors at McMaster University, this book describes the principles of measurement, developed in education and psychology, for a health sciences audience. The book discusses both traditional topics in measurement, eg item selection and reliability, and contemporary topics such as generalizability theory and latent tract theory, covering all the steps necessary in developing a new measurement scale, from the initial literature search to the design and analysis of reliability and validity studies. Many of the standard topics are addressed using a minimum of algebra and technical vocabulary. Although the examples are drawn from health sciences, the book should also be useful to all students of measurement in the social and behavioural sciences.