The IRT Procedure

ODS Graphics

Statistical procedures use ODS Graphics to create graphs as part of their output. ODS Graphics is described in detail in ChapterĀ 21: Statistical Graphics Using ODS.

Before you create graphs, ODS Graphics must be enabled (for example, by specifying the ODS GRAPHICS ON statement). For more information about enabling and disabling ODS Graphics, see the section Enabling and Disabling ODS Graphics in ChapterĀ 21: Statistical Graphics Using ODS.

The overall appearance of graphs is controlled by ODS styles. Styles and other aspects of using ODS Graphics are discussed in the section A Primer on ODS Statistical Graphics in ChapterĀ 21: Statistical Graphics Using ODS.

You must also specify the PLOTS= option in the PROC IRT statement.

PROC IRT assigns a name to each graph that it creates using ODS. You can use these names to refer to the graphs when using ODS. The names are listed in Table 65.5.

Table 65.5: Graphs Produced by PROC IRT

ODS Graph Name

Plot Description

PLOTS= Option

ItemCharCurve

Item characteristic curves

PLOTS =ICC. The plot panels by default; specify PLOTS=UNPACK to produce an individual plot for each item.

ItemInfoCurve

Item information curves

PLOTS =IIC. The plot panels by default; specify PLOTS=UNPACK to produce an individual plot for each item.

PolyCorrHeatMap

Heat map for polychoric correlation matrix

PLOTS =POLYCHORIC|PLCORR

ScreePlot

Scree and variance-explained plots

PLOTS =SCREE

TestInfoCurve

Test information curve

PLOTS =TIC

VariancePlot

Plot of explained variance

PLOTS =SCREE(UNPACK)