dexter (version 1.5.0)

DIF: Exploratory test for Differential Item Functioning

Description

Exploratory test for Differential Item Functioning

Usage

DIF(dataSrc, person_property, predicate = NULL)

Value

An object of class DIF_stats holding statistics for overall-DIF and a matrix of statistics for DIF in the relative position of item-category parameters in the beta-parameterization where they represent locations on the ability scale where adjacent categories are equally likely. If there is DIF, the function `plot` can be used to produce an image of the pairwise DIF statistics.

Arguments

dataSrc

a connection to a dexter database or a data.frame with columns: person_id, item_id, item_score

person_property

Defines groups of persons to calculate DIF

predicate

An optional expression to subset data, if NULL all data is used

Details

Tests for equality of relative item/category difficulties across groups. Supplements the confirmatory approach of the profile plot.

References

Bechger, T. M. and Maris, G (2015); A Statistical Test for Differential Item Pair Functioning. Psychometrika. Vol. 80, no. 2, 317-340.

See Also

A plot of the result is produced by the function plot.DIF_stats

Examples

 RcppArmadillo::armadillo_throttle_cores(1)

db = start_new_project(verbAggrRules, ":memory:", person_properties=list(gender='unknown'))
add_booklet(db, verbAggrData, "agg")
dd = DIF(db,person_property="gender")
print(dd)
plot(dd)
str(dd)

close_project(db)

 RcppArmadillo::armadillo_reset_cores()