Package: irtlink 0.1.0

irtlink: IRT Linking and Linking Error Estimation Across Time Points and Groups

Estimation of trends in the mean and standard deviation of latent ability distributions across the time points of educational assessments, and of ability distribution differences across linked groups, for unidimensional item response theory (IRT) models (1PL, 2PL, 3PL, partial credit, and generalized partial credit). Groups connected through common items, with independent or dependent person samples, are calibrated on an internal marginal maximum likelihood EM engine, separately, concurrently, with fixed item parameters, or with regularized calibration. Linking methods include mean-mean and mean-geometric mean linking, Haberman linking (Haberman, 2009, <doi:10.1002/j.2333-8504.2009.tb02197.x>) with robust Lp loss and a pairwise variant (Robitzsch, 2025, <doi:10.3390/appliedmath5010007>), and the response function methods of Haebara and Stocking-Lord. Under differential item functioning (DIF), the linked estimates depend on the selected common items, and the package estimates this linking error together with the standard error by jackknife and sandwich estimators, including bias-corrected variants (Robitzsch, 2024, <doi:10.3390/stats7030036>). RMSD and likelihood-ratio DIF diagnostics with iterative purification are included.

Authors:Oskar Engels [aut, cre]