Item Analysis

Summary: Perform item analysis using a 2-Parameter Logistic (2PL) model and visualize the results with dual plots, setting scale and reference lines.

Code:

// Open data table
dt = Open("$Sample_Data/MathScienceTest.jmp");
// Item Analysis
Item Analysis(
    Y(
        :Q1, :Q2, :Q3, :Q4, :Q5, :Q6, :Q7,
        :Q8, :Q9, :Q10, :Q11, :Q12, :Q13,
        :Q14
    ),
    Model( "Logistic 2PL" ),
    Number of Plots Across( 2 ),
    SendToReport(
        Dispatch( {"Dual Plot"}, "1",
            ScaleBox,
            {Scale( "Linear" ),
            Format( "Fixed Dec", 1 ),
            Min( 0 ), Max( 2 ),
            Inc( 0.5 ), Minor Ticks( 1 ),
            Add Ref Line(
                1, "Dotted", "Black"
            )}
        ),
        Dispatch( {"Dual Plot"}, "2",
            ScaleBox,
            {Scale( "Linear" ),
            Format( "Best" ), Min( -4 ),
            Max( 4 ), Inc( 1 ),
            Minor Ticks( 7 )}
        )
    )
);