The IRT Procedure
-
Overview
- Getting Started
-
Syntax
-
DetailsNotation for the Item Response Theory ModelAssumptionsPROC IRT Contrasted with Other SAS ProceduresResponse ModelsMarginal LikelihoodApproximating the Marginal LikelihoodMaximizing the Marginal LikelihoodFactor Score EstimationModel and Item FitItem and Test informationMissing ValuesOutput Data SetsODS Table NamesODS Graphics
-
Examples
- References
ODS Graphics
Statistical procedures use ODS Graphics to create graphs as part of their output. ODS Graphics is described in detail in Chapter 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 Chapter 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 Chapter 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) |