Testiteoria

Testiteoria, or test theory, is a branch of psychometrics that studies the design, analysis, and interpretation of tests used to measure psychological attributes and educational achievement. It aims to quantify latent traits such as ability, attitude, or personality and to convert observable responses into meaningful scores while accounting for measurement error.

Classical Test Theory (CTT) provides foundational concepts. It models an observed score as the sum of a true score and an error term. Reliability refers to the consistency of test scores, and the standard error of measurement expresses precision. Validity concerns whether a test measures the intended construct, including content validity, criterion-related validity, and construct validity. Item analysis examines item difficulty and discrimination to improve test quality.

Modern approaches include Item Response Theory (IRT) and Rasch models. IRT links item properties and respondent traits, yielding item characteristic curves and ability estimates that are relatively independent of the specific sample. The Rasch model is a one-parameter IRT model with strong measurement properties. Test information and standard errors vary across levels of the trait, and computerized adaptive testing uses this information to tailor item sequences.

Applications of testiteoria include test construction and scaling, score interpretation, and statistical equating and linking of scores from different test forms. It also addresses measurement invariance and fairness across groups, accessibility, and bias, guiding ethical assessment practices.

History and development trace to early 20th-century psychology, with contributions from researchers such as Spearman and Thorndike, advancing reliability and validity concepts, and culminating in modern CTT and IRT frameworks through the mid- to late 20th century.