This classic volume outlines, for both students and professionals, the mathematical theories and equations that are necessary for evaluating a test and for quantifying its characteristics. The author utilizes formulas that evaluate both the reliability and the validity of tests. He also provides the means for evaluating the reliability and validity of total test scores and individual item analysis. The work remains one of the only books on classical test theory to discuss applications, "true score" theory, the effect of test length on reliability and validity, and the effects of univariate and multivariate selection on validity.