In this newly updated Fourth Edition, new terms are defined, new synonyms are included, and both are illustrated with new graphics. Growth in the fields of statistics and methodology has mandated these inclusions. The number of definitions and illustrations has grown from about 2,400 in the third edition to about 2,800 in this one, an increase of around 16 percent. While some entries have been shortened and obsolete ones have been deleted, which helped make room for the new entries, comparatively few terms from the earlier editions have been deleted. The importance of classic terms persists even as new techniques and the terms describing them are invented. Finally, the suggestions for further reading have been updated and a new section on Useful Websites on Statistics and Methodology has been added.