This book provides an introduction to a rapidly-growing area in the social and behavioral sciences -- the modeling of systems in which one or more variables are hypothesized, but not directly observed. Providing a conceptually unified treatment of modeling of this type -- exploratory and confirmatory factor analysis, path analysis, and structural equation analysis -- it is intended to introduce these techniques to individuals who have had some exposure to statistical methods in general, but are beginners in this particular area. Using an inductive and informal approach, it emphasizes the use of path diagrams and a variety of concrete examples, and keeps the mathematics largely intuitive. Examples are drawn from a variety of fields, including psychometrics, sociology, psychology, education and behavior genetics. Although some introductory material is provided for LISREL, EQS, and CALIS, and for exploratory factor analysis programs in SAS, SPSS, and BMPD, the book is not closely tied to any one computer program or statistical package.