ITEM RESPONSE THEORY FOR SCORES ON TESTS INCLUDING POLYTOMOUS ITEMS WITH ORDERED RESPONSES

Item response theory (IRT) provides procedures for scoring tests inclu ding any combination of rated constructed-response and keyed multiple- choice items, in that each response pattern is associated with some mo dal or expected a posteriori estimate of trait level. However, various considerations that frequently arise in large-scale testing make resp onse-pattern scoring an undesirable solution. Methods are described ba sed on IRT that provide scaled scores, or estimates of trait level, fo r each summed score for rated responses, or for combinations of rated responses and multiple-choice items. These methods may be used to comb ine the useful scale properties of IRT-based scores with the practical virtues of a scale based on a summed score for each examinee.