Although the goals and procedures of statistical research have changed little since the Third Edition of Statistics for Research (by Dowdy) was published, the almost universal availability of personal computers and statistical computing application packages have made it possible for today's statisticians to do more in less time than ever before. The Fourth Edition of this bestselling text reflects how the changes in the computing environment have transformed the way statistical analyses are performed today. Based on extensive input from university statistics departments throughout the country, the authors have made several important and timely revisions, including the extensive integration of "R" subroutines as the computer package of choice throughout the text and the addition of material on mixed models, unbalanced designs, missing observations, error term diagnostics, and modern methods of variable selection, among others. The text features the most commonly used statistical techniques for the analysis of research data. As in the earlier editions, emphasis is placed on how to select the proper statistical procedure and how to interpret results. Whenever possible, to avoid using the computer as a "black box" that performs a mysterious process on the data, actual computational procedures are also given.