Modeling and Multivariate Methods - SAS

530 Scoring Tests Using Item Response Theory Chapter 22
Item Analysis Output
Item Analysis Output
The following plots appear in Item Analysis reports.
Characteristic Curves
Item characteristic curves for each question appear in the top section of the output. Initially, all curves are
shown stacked in a single column. They can be rearranged using the Number of Plots Across command,
found in the drop down menu of the report title bar. For Figure 22.8, four plots across are displayed.
Figure 22.8 Component Curves
A vertical red line is drawn at the inflection point of each curve. In addition, dots are drawn at the actual
proportion correct for each ability level, providing a graphical method of judging goodness-of-fit.
Gray information curves show the amount of information each question contributes to the overall
information of the test. The information curve is the slope of the ICC curve, which is maximized at the
inflection point.