Models for Dichotomous Items
The simplest items in achievement testing have only two different outcomes, correct and incorrect. These items are dichotomous. If an examinee does not answer an item, we evaluate the nonresponse as incorrect. A correct answer can be assigned a score 1, and an incorrect answer can be assigned a score 0 (see Exhibit 6.1). Dichotomous items are frequently used in tests. For example, achievement, aptitude, and intelligence tests with multiple-choice items are frequently scored dichotomously. For dichotomous and dichotomized items, test models have been developed to account for the scores of persons on such tests.