The IRT Procedure

The VAR statement lists the analysis variables or items in the model. If you do a multiple-group analysis, the same set of analysis variables is assumed for all groups. By default, all variables that you specify in the VAR statement are fitted by the graded response model, which assumes that the analysis variables are ordinal and have 2 to 19 levels.

You can overwrite the default response model for the analysis variables in the VAR statement by using the RESFUNC= option in the PROC IRT statement. If you want to analyze the data by using a mixed type of response model, you can use the MODEL statement.