New Developments in Mokken Scale Analysis in R

Mokken (1971) developed a scaling procedure for both dichotomous and polytomous items that was later coined Mokken scale analysis (MSA). MSA has been developed ever since, and the developments until 2000 have been implemented in the software package MSP (Molenaar and Sijtsma 2000) and the R package mokken (Van der Ark 2007). This paper describes the new developments in MSA since 2000 that have been implemented in mokken since its first release in 2007. These new developments pertain to invariant item ordering, a new automated item selection procedure based on a genetic algorithm, inclusion of reliability coefficients, and the computation of standard errors for the scalability coefficients. We demonstrate all new applications using data obtained with a transitive reasoning test and a personality test.