This book provides a practical overview of the statistical methods used in quality control and quality assurance in medical diagnosis, including their applications in clinical and radiological laboratories as well as central laboratories in multi-center clinical trials. The book consists of 10 chapters, covering topics of an overview of quality assurance and quality control practice, precision, accuracy, and agreement of continuous measures, longitudinal monitoring equipment performance and process control, calibration and upgrade of equipments, reader agreement in categorical variables, examples of quality control on disease diagnosis and clinical trials, diagnostic sensitivities, etc. It is intended for statistical readers as well as clinical readers who are interested in related statistical methods.