Estimation/smoothing methods that are flexible enough to fit a wide variety of test score distributions are reviewed: kernel method, strong true-score model-based method, and method that uses polynomial log-linear models. Applications of these methods include describing/comparing test score distributions, estimating norms, and estimating…

A testlet is an integrated group of test items presented as a unit. The concept of testlet differential item functioning (testlet DIF) is defined, and a statistical method is presented to detect testlet DIF. Data from a testlet-based experimental version of the Scholastic Aptitude Test illustrate the methodology. (SLD)