The primary purpose of this book is to introduce the reader to elementary statistical methods as related to tests of differences, such as one-sample tests, tests of two independent samples, tests of two matched samples, and one-way analysis of variance. Throughout the book the emphasis is on permutation statistical methods, although the results of the permutation analyses are always compared and contrasted with the results of conventional statistical analyses. Unlike classical statistical methods, permutation statistical methods do not rely on theoretical distributions, avoid the usual assumptions of normality and homogeneity, depend only on the observed data, and do not require random sampling. The book is designed for an audience with limited statistical background and can easily serve as a supplementary textbook in an undergraduate or graduate course in departments such as statistics, psychology, economics, or biology. In particular, the audience for this book is quantitative undergraduate and graduate students in fields such as psychology, sociology, biology and political science. No statistical training beyond a first course in statistics is required.