Item Response Theory With Covariates (IRT-C)

IRT-FIT: SAS® Macros for Fitting Item Response Theory (IRT) Models

Psychometrics has recently seen the development of complex measurement models to better represent test and item data. Item Response Theory (IRT), in particular, comprises a set of non-linear latent variable models that appear to have several conceptual and empirical properties that make them more valuable in practice than classical test theory methods. However, IRT-based models typically requir...

Re-evaluating a vision-related quality of life questionnaire with item response theory (IRT) and differential item functioning (DIF) analyses

BACKGROUND For the Low Vision Quality Of Life questionnaire (LVQOL) it is unknown whether the psychometric properties are satisfactory when an item response theory (IRT) perspective is considered. This study evaluates some essential psychometric properties of the LVQOL questionnaire in an IRT model, and investigates differential item functioning (DIF). METHODS Cross-sectional data were used f...

Applications of Multidimensional Item Response Theory Models With Covariates to Longitudinal Test Data

GOF OF IRT MODELS 1 Goodness of fit assessment of item response theory models

The article provides an overview of goodness of fit assessment methods for item response theory (IRT) models. It is now possible to obtain accurate p-values of the overall fit of the model if bivariate information statistics are used. Several alternative approaches are described. As the validity of inferences drawn on the fitted model depends on the magnitude of the misfit, if the model is reje...

Investigate into Invariance Properties of Item Response Theory (irt) by Two and Three Parameter Models

Despite the well-known theoretical differences between item response theory (IRT) and classical test theory (CTT), research examining their empirical properties has failed to reveal consistent, demonstrable differences due to usage of samples with errors, incorrect assumptions & incorrect calculations. Dr. Natarajan (India, 1984) had proved the item invariance with his classic 20 X 76 test data...