This text was developed on an autoinstructional basis to familiarize the reader with the various interpretations of reliability and validity, their measurement and evaluation, and factors influencing their measurement. The text enables those with prior knowledge of statistics to increase their understanding of variance and correlation. Review exercises and references to other texts are provided for those who have no statistical background. Upon completion of the book, the student should be capable of studying the concepts of validity and reliability at more advanced levels, and of evaluating the reported reliabilities and validities of commercial or standardized tests in terms of their adequacy and relevance for his purposes. A bibliography and indexes are included. (CK)