ERIC Number: ED255540
Record Type: Non-Journal
Publication Date: 1984-Nov
The Graphical Display of Simulation Results, with Applications to the Comparison of Robust IRT Estimators of Ability.
Thissen, David; Wainer, Howard
Simulation studies of the performance of (potentially) robust statistical estimation produce large quantities of numbers in the form of performance indices of the various estimators under various conditions. This report presents a multivariate graphical display used to aid in the digestion of the plentiful results in a current study of Item Response Theory (IRT) ability estimators. Called XTREE, or the "Christmas Tree Glyph," the display has a vertical line or "trunk" with angled lines or "branches" for each estimator which display bias (left) and random variance (right). The sum of the two branch lengths represents the mean square error (MSE). Appendix A is a tabular presentation of the results to illustrate the data interpretation problem. Appendix B contains the XTREE computer programs (written in FORTRAN IV for a Honeywell DPS computer system and a Hewlett-Packard 7470A plotter). (Author/BS)
Publication Type: Reports - Research; Computer Programs
Education Level: N/A
Sponsor: Air Force Human Resources Lab., Brooks AFB, TX.
Authoring Institution: Educational Testing Service, Princeton, NJ. Program Statistics Research Project.