Table 2

True positive and false positive rates as a function of generating IRT model, DIF size, number of DIF items, and mean difference between modes
IRT Model DIF Size DIF % Diff. Mean θ Robust Z Bayes 95% CrI
TP% FP% TP% FP%
1PL 0.42 10 0 54.90 0.91 60.35 1.36
1 70.00 2.36 66.35 3.88
30 0 69.66 0.29 70.67 0.44
1 71.09 1.05 71.91 2.58
0.63 10 0 78.00 0.56 83.00 0.89
1 75.00 3.56 81.00 5.22
30 0 82.67 2.57 87.00 3.00
1 76.33 2.14 79.33 3.29
2PL 0.42 10 0 60.82 0.06 60.42 0.06
1 58.24 2.09 55.10 3.89
30 0 62.71 0.14 66.09 0.28
1 66.00 4.86 66.33 6.86
0.63 10 0 72.00 0.33 77.00 0.55
1 70.00 2.39 77.00 3.56
30 0 72.33 3.14 77.67 3.14
1 66.33 3.33 69.00 5.00
Average 69.13 1.86 71.76 2.75

1PL = one-parameter item response model; 2PL = two-parameter item response model; CAT = computerized adaptive testing; DIF = differential item functioning; DIF% = percentage of items simulated with DIF; FP% = percentage of false positive DIF results; IRT = item response theory; TP% = percentage of true positive DIF results; θ = person measure.

Riley and Carle

Riley and Carle BMC Medical Research Methodology 2012 12:124   doi:10.1186/1471-2288-12-124

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