This is the new edition of the highly successful practical guide for clinicians developing tools to measure subjective states, attitudes or non-tangible outcomes in their patients. It is widely used by people from many disciplines, who have only a limited knowledge of statistics.This thoroughly updated edition of Health Measurement Scales 3e gives more details on cognitive requirements in answering questions, and how this influences scale development. There is now an expanded discussion of generizibility theory, a completely revised chapter on Item Response Theory and many revisions are included, based on the latest research findings.These features combine to provide the most up-to-date guide to measuring scale development available. It synthesizes the theory of scale construction with practical advice, culled from the literature and the authors' experience, about how to develop and validate measurement scales to be used in the health sciences. The theory goes into issues of reliability, generalizability theroy, validity, the measurement of change, the cognitive requirements of answering questions, and item response theory. Practical issues cover devising the items, biases that may affect the responses, pre-testing and weeding our poorly performing items, combining items into scales, setting cut points, and the practical issues of using scales in various ways, such as face-to-face interviews; mailed or telephone-administered surveys; and over the internet. One chapter also discusses some of the ethical issues that scale developers and users should be aware of. Appendices lead the reader to other readings; sources of already developed scales and items; and a very brief introduction to exploratory and confirmatory factor analysis.