Book excerpt: This text has been named as an approved reference in preparing for the SOA Exam C and the CAS Exam 4. Several chapters have been adopted as syllabus references for the SOA Group and Health specialty Design and Pricing Fellowship exam. Credibility modeling is a proven approach for analyzing unique product designs. This text presents a wide variety of credibility models in an easy-to-read style, and in so doing, traces the historical development of the subject. The Bayesian approach to credibility is emphasized. The text concentrates on basic statistical concepts, leaving more sophisticated theoretical concepts for a more advanced treatment elsewhere. It contains worked examples, a large number of end-of-chapter exercises and an extensive bibliography. Practical applications of credibility theory are presented in the Appendices. In the rapidly evolving healthcare environment, data credibility is more important than ever. The Fourth Edition of this text includes three case studies relating to healthcare issues. A separate solutions manual for the text exercises is also available.