Applying Item Response Theory Methods to Examine the Impact of Different Response Formats

In aptitude and achievement tests, different response formats are usually used. A fun-damental distinction must be made between the class of multiple-choice formats and the constructed response formats. Previous studies have examined the impact of dif-ferent response formats applying traditional statistical approaches, but these influen-ces can also be studied using methods of item response theory to deal with incomplete data. Response formats can influence item attributes in two ways: differ-ent response formats could cause items to measure different latent traits or they could contribute differently to item difficulty. In contrast to previous research, the present study examines the impact of response formats on item attributes of a lan-guage awareness test applying different item response theory models. Results indi-cate that although the language awareness test contains items with different response formats, only one latent trait is measured; no format-specific dimensions were found. Response formats do, however, have a distinct impact on the difficulty of the items. In addition to the effects of the three administered item types, a fourth component that makes items more difficult was identified