The Person Response Curve: Fit of Individuals to Item Response Theory Models

Publisher Summary This chapter discusses the feasibility of the person response curve (PRC) approach for investigating the fit of persons to the three-parameter item response theory (IRT) model. To operationalize the PR,C it subdivides ability test items into separate strata of varying difficulty levels. The limited literature on person variability within a test, thus, seems to have three major trends: (1) the direct analysis of person variability as originally suggested by Mosier, later called the testee's trace line by Weiss, the subject characteristic curve by Vale and Weiss, and the person characteristic curve by Lumsden, (2) the designation of highly variable persons as aberrant by Levine and Rubin, (3) the elimination of aberrant person-item interactions by Wright. A careful analysis of these three approaches indicates that the first approach is the most general of the three, subsuming the other two as special cases: If the entire pattern of a testee's responses is studied as a function of the difficulty levels of the items, the identification of aberrant response patterns or person–item interactions follows directly. In addition, postulating a person characteristic curve in conjunction with IRT provides a means of testing whether the response patterns of single individuals fit the theory, regardless of the number of parameters assumed.