item_fit {IRTest}

Item fit diagnostics

Description

This function analyzes and reports item-fit test results.

Usage

item_fit(x, bins = 10, bin.center = "mean")

Arguments

x

A model fit object from either IRTest_Dich, IRTest_Poly, or IRTest_Mix.

bins

The number of bins to be used for calculating the statistics. Following Yen's Q_{1} (1981), the default is 10.

bin.center

A method for calculating the center of each bin. Following Yen's Q_{1} (1981), the default is "mean". Use "median" for Bock's \chi^{2} (1960).

Details

Bock's \chi^{2} (1960) or Yen's Q_{1} (1981) is currently available.

Value

This function returns a matrix of item-fit test results.

Author(s)

Seewoo Li [e-mail]

References

Bock, R.D. (1960), Methods and applications of optimal scaling. Chapel Hill, NC: L.L. Thurstone Psychometric Laboratory.

Yen, W. M. (1981). Using simulation results to choose a latent trait model. Applied Psychological Measurement, 5(2), 245–262.

Examples

# A preparation of dichotomous item response data

data <- DataGeneration(N=500,
                       nitem_D = 10)$data_D

# Analysis

M1 <- IRTest_Dich(data)

# Item fit statistics

item_fit(M1)