Appropriate interpretation of assessment data requires an appreciation that tools are subject to measurement error. School psychologists recognize, at least on an intellectual level, that measures are imperfect--that test scores and other quantitative measures (e.g., rating scales, systematic behavioral observations) are best estimates of…

The latest edition of this perennial bestseller instructs and updates students and clinicians on the basic principles of psychological assessment and measurement, recent changes in assessment procedures, and the most widely used tests in counseling practice today. Dr. Danica Hays guides counselors in the appropriate selection, interpretation, and…

Item response theory (IRT) methodology is introduced as a tool for improving assessment instruments used with people who have disabilities. Need for this approach in rehabilitation is emphasized; differences between IRT and classical test theory are clarified. Concepts essential to understanding IRT are defined, necessary data assumptions are…