National Cancer Institute

Involving: Mark Wilson, Jun Corser Li, Tzur Karelitz, and Diane Allen.

The project related to the National Cancer Institute is to show how item response modeling techniques might be of use to behavioral scientists, since little IRM has been applied in this area to date. Patient-reported attitudes and outcomes are of particular interest to behavioral scientists, especially when trying to determine the mediating or moderating effects of self-efficacy, self-regulation of motivation, and decisional balance, for example, on behavior change that occurs after intervention. The institute provided the data sets and a few references regarding the instruments used, and some ideas about what analyses might be of interest. Since the data were all collected prior to the involvement of IRM analysts, exploration of the data in various configurations was required, and some less than ideal circumstances had to be acknowledged (e.g., wording changes within items across sites). The intent of this group was to determine which data sets best illustrated the principles and benefits of IRM techniques, and report the analyses in a way that could be well understood by an audience having little experience with IRM. Three presentations at a conference in June, 2004, and several papers have resulted from this group. The presentations and papers introduce IRM using the NCI data, and demonstrate, for example, instrument evaluation, multidimensional analysis, equating, and DIF analyses.