Item-total regressions for the Rasch vs. the interaction model

Description

Compare the item-total regressions fit by the Rasch model and the interaction model, for one, several, or all items in the test.

Usage

1
rim(x, items = NULL, showData = FALSE, shade = 10, ncol = 3, ...)

Arguments

x

A matrix of scored responses (persons in rows, items in columns)

items

The items to plot (column numbers). If NULL, all items will be plotted

showData

If TRUE, the observed proportion correct at each sum score will be shown on the plot. Default is FALSE (show only the regressions)

shade

The part of the probability mass for the sum scores to shade out, shown as percentage. Default is 10: shade the most extreme 10 Ignored when add=TRUE.

ncol

When plotting multiple items, the user can suggest the number of columns in the matrix of plots (up to 3, will be adjusted if necessary)

...

Any additional plotting parameters

Author(s)

Ivailo Partchev, using theory and C code by Gunter Maris

See Also

interactionModel

Examples

1
rim(Scored, items=2)

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