The assessment of test data for the presence of differential item functioning (DIF) is a key component of instrument development and validation. Among the many methods that have been used successfully in such analyses is the mixture modeling approach. Using this approach to identify the presence of DIF has been touted as potentially superior for…

In aptitude and achievement tests, different response formats are usually used. A fundamental distinction must be made between the class of multiple-choice formats and the constructed response formats. Previous studies have examined the impact of different response formats applying traditional statistical approaches, but these influences can also…

The article compares three different methods to estimate effects of task characteristics and to use these estimates for model-based proficiency scaling: prediction of item difficulties from the Rasch model, the linear logistic test model (LLTM), and an LLTM including random item effects (LLTM+e). The methods are applied to empirical data from a…