Graphical Representation of Multidimensional Item Response Theory Analyses

This paper illustrates how graphical analyses can en hance the interpretation and understanding of multidi mensional item response theory (IRT) analyses. Many unidimensional IRT concepts, such as item response functions and information functions, can be extended to multiple dimensions; however, as dimensionality in creases, new problems and issues arise, most notably how to represent these features within a multidimen sional framework. Examples are provided of several dif ferent graphical representations, including item response surfaces, information vectors, and centroid plots of con ditional two-dimensional trait distributions. All graphs are intended to supplement quantitative and substantive analyses and thereby assist the test practitioner in deter mining more precisely such information as the construct validity of a test, the degree of measurement precision, and the consistency of interpretation of the number- correct score scale.