Research On Examinees' Ability Assessments In Models Composed Of Both Dichotomous And Polytomous Items And Simulation Comparisons

Mixed-type model is a new member of the item response theory's family,Its generation and development provided a wider application for item response theory.For mixed-type tests composed of both dichotomous and polytomous items,polytomous items often yield more information than dichotomous ones.To reflect the difference between that two types of items,polytomous items are usually pre-assigned with larger weights.Assuming the item parameters are known,research on examinees' ability assessments in three mixed-type models are respectively composed of two-parameter logistic model,three-parameter logistic model,four-parameter logistic model and generalized partial credit model.The evaluation and comparison of various estimation methods are carried out through simulation.Simulation results show that the estimated ability based on the new procedure is more consistent with examinee's true ability.In other words,weighted likelihood method is superior to maximum likelihood method.