Distinguishing differences in construct from differences in response style: gsem models for Item-Response Theory Models with Anchoring Vignettes

Item response theory (IRT) models allow estimation of participant and group mean trait scores from responses to a set of items, but estimates can be biased when participants vary in their response style. We illustrate models estimated in gsem that can account for suchresponse style differences by comparing self-report with their ratings of anchoring vignettes - descriptions of other individuals displaying different levels of the trait. Simulation results from standard IRT, mean bias, random bias and free-threshold models are illustrated. We show that unbiased estimates can be recovered where the vignettes rated depend on the participants own self-rating or even rated