This book presents an up-to-date, accessible, and authoritative look into the rapidly emerging study of statistical adaptive design. Employing the R language throughout, it emphasizes the usefulness of adaptive design methods and technology in public health and research settings through practical examples and plentiful exercises. Special focus is on adaptive late-stage clinical trial designs as extensions of the highly successful group sequential methods that have been applied for more than two decades. It is the first elementary text on the subject matter that is aimed at clinicians, investigators, credit rating analysts, medical writers, regulatory affairs specialists, and applied statisticians.