This book has three distinctive features. First, it stresses the basic logic of psychological assessment without getting bogged down with mathematics; the spreadsheet simulations and utilities which are integrated into the text allow users to explore how numbers behave, rather than reading equations. Readers will "learn by doing". Second, it covers both the theory behind psychological assessment and the practicalities of locating, designing and using tests and interpreting their scores. Finally, it is evaluative. Rather than just describing concepts such as test reliability or adaptive testing, it stresses the underlying principles, merits and drawbacks of each approach to assessment, and methods of developing and evaluating questionnaires and tests. Unusually for an introductory text, it includes coverage of several cutting-edge techniques, and this new edition expands the discussion on measurement invariance, methods of detecting/quantifying bias and hierarchical factor models, and features added sections on: Aimed at non-mathematicians, this friendly and engaging text will help you to understand the fundamental principles of psychometrics that underpin the measurement of any human characteristic using any psychological test. Written by a leading figure in the field and accompanied by additional resources, including a set of spreadsheets which use simulated data and other techniques to illustrate important issues, this is an essential introduction for all students of psychology and related disciplines. It assumes very little statistical background and is written for students studying psychological assessment or psychometrics, and for researchers and practitioners who use questionnaires and tests to measure personality, cognitive abilities, educational attainment, mood or motivation.