The data set is simulated from a Partial Credit Model where some items exhibit differential item functioning. Existing differences in item difficulties are simulated by step-functions. The true, simulated DIF structure is described in Bollmann et al. (2017), Section 4.3.
A data frame containing 500 observations on 4 variables:
Y matrix with categorical responses (3-point scale)
x1 binary covariate
x2 ordinal covariate
x3 numeric covariate
Bollmann, Stella, Berger, Moritz & Tutz, Gerhard (2018): Item-Focussed Trees for the Detection of Differential Item Functioning in Partial Credit Models, Educational and Psychological Measurement 78(5), 781-804.
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