iccfit function

Item Characteristic Curve Fitting

Plots the item characteristic curve and the simulated observed proportions of correct response from the one-, two-, or three-parameter logistic model.

iccfit(mdl)

Arguments

• mdl: 1, 2, or 3 representing the number of the model parameters.

Details

While the theoretical range of ability is from negative infinity to positive infinity, practical considerations usually limit the range of values from -3 to +3. With the number of item characteristic curve model parameters mdl

the item parameters are randomly sampled from the uniform distributions; for example, under the three-parameter logistic model, b from the -3 to 3 range, a from the 0.2 to 2.8 range, and c from the 0 to .35 range. Each of the 33 ability levels from the -3 to +3 range with .1875 interval, the observed proportion of correct response is generated from the binomial distribution for sample size of 21. The chi-square goodness-of-fit index is obtained and reported with the set of item parameters.

Examples

iccfit(1)
iccfit(2)
iccfit(3)

References

Baker, F. B., & Kim, S.-H. (2017). The basics of item response theory using R.

New York, NY: Springer. ISBN-13: 978-3-319-54204-1