This textbook is designed for the population of students we have encountered while teaching a two-semester introductory statistical methods course for graduate students. These students come from a variety of research disciplines in the natural and social sciences. Most of the students have no prior background in statistical methods but will need to use some, or all, of the procedures discussed in this book before they complete their studies. Therefore, we attempt to provide not only an understanding of the concepts of statistical inference but also the methodology for the most commonly used analytical procedures.