The second edition includes a series of 16 volumes (in-print) and a continuously updated product on-line. The first edition is considered the authoritative reference in statistics with extensive coverage of statistical theory, methods, and applications. Three important tasks are accomplished in this second edition: (1) description of new topics in the statistical literature; (2) detailing of methods and applications that have gained prominence since the first edition; and (3) reposition of gaps in coverage provided by previous volumes. In addition to the main selections, which feature fascinating discussions of developments in various branches of the statistical sciences, readers will find a series of shorter entries ranging in subject matter from the lives of pioneers in statistics to updates of popularly-held methodologies and reviews of statistical agencies and journals. Up-to-date bibliographies and thorough cross-referencing facilitate quick access to specific information and provide an indispensable platform for further study and research. A cumulative and comprehensive index appears in the last volume and in the form of a powerful search engine in the on-line version. There is a substantial increase in the number of contributions outside North America and the United Kingdom, as well as an increase in the number of female authors. There are more than 3,000 combined authorships, spanning five continents in over 30 countries.