Extended Graphical Model Checks for the Rasch Family of Models

The function plotLRT() draws pairwise graphical model checks for the Rasch Model (RM; Rasch, 1960), the Partial Credit Model (PCM; Masters, 1982), and the Rating Scale Model (RSM; Andrich, 1978) using the output object of eRm::LRtest(). The function cLRT() provides a conditional Likelihood Ratio Test (Andersen, 1973), using the routines of 'psychotools' (Zeileis et al., 2026). Users may choose to plot the threshold parameters, the cumulative thresholds, the average thresholds per item, or the person parameters. Extended coloring options allow for automated item-wise or threshold-wise coloring. For multi-group splits, all pairwise group comparisons are drawn automatically. The function plotMLT() draws a graphical model check for the Martin-Loef-Test (MLT). If type='persons', it draws scatterplots of the person parameter estimates of each pair of item sub-groups. If type='items', it draws a scatterplot of the item/threshold parameter estimates of each of the two sub-groups vertically against the estimates of the total sample horizontally.