Complete response vectors of all answer options in multiple-choice items can be used to estimate ability. The rising selection ratios criterion is necessary for scoring individuals because it implies that estimated ability always increases when the correct alternative is selected. This paper introduces the generalized
DLT model, which assumes rising selection ratios and uses three parameters to describe each incorrect alternative. It is shown that the nominal categories and the Thissen and Steinberg model do not meet the criterion. A simulation study on goodness of recovery and an example with real data are also included.
Keywords multiple-choice items - nominal data - rising selection ratio - DLT - nominal categories model - Thissen & Steinberg model.
This research was partially supported by the DGICYT grant PB 97-0049 and the Comunidad de Madrid grant 06/HSE/0005/2004. I would like to express my gratitude to three anonymous reviewers, the associate editor and two editors for their helpful and thoughtful comments that contributed for improving an earlier version of the manuscript.
This revised article was published online in June 2005 with all corrections incorporated.