Have you ever wondered if birth order effects vary across ethnic groups, or whether a particular clinical intervention is likely to yield dissimilar outcomes for men and women? This book provides practical guidance for using a statistical tool known as moderated multiple regression (MMR) to assess whether the relationship between two quantitative variables is moderated by group membership. Included are discussions and fully worked-out examples of how to conduct and interpret MMR analysis, as well as descriptions of computer programs that can be used to check the accuracy of results. Assuming only a basic knowledge of inferential statistics on the part of the reader, this is an essential hands-on guide for students, researchers, and practitioners. Together with its associated computer programs and data sets (available on the Web), the book will also serve as an invaluable supplemental text in advanced undergraduate statistics and methods courses and in graduate courses addressing the general linear model.