Table 2. McFadden’s pseudo R2 and IRT parameters for items displaying DIF.
Item bank | Item with DIF | DIF type | McFadden’s pseudo R2 | Slope; and threshold parameters | Included in CATd |
---|---|---|---|---|---|
Anxiety | EDANX03: It scared me when I felt nervous | Uniform | R212 = 0.021 R223 = 0.011 | NL: 2.62; 0.15, 0.97, 2.02 | 1% |
US: 3.74; 0.59, 1.18, 1.95 | |||||
EDANX30: I felt worrieda | Non-uniform | R212 = 0.010 R223 = 0.033 | NL: 2.16; -1.12, -0.10, 1.29, 2.64 US: 3.14; -0.57, 0.24, 1.22, 2.12 | 3% | |
Depression | EDDEP04: I felt worthlessb | Uniform | R212 = 0.024 R223 = 0.013 | NL: 2.93; -0.17, 0.58, 1.56, 2.61 US: 4.37; 0.29, 0.88, 1.61, 2.36 | 8% |
EDDEP36: I felt unhappyc | Uniform | R212 = 0.037 R223 = 0.001 | NL: 4.21; -0.14, 0.61, 1.33, 2.20 US: 3.44; -0.64, 0.23, 1.20, 2.17 | 100% |
The bold population had lower thresholds compared to the other population, indicating that this population endorses higher item response categories at the same level of the domain (anxiety, depression)
a present in the anxiety 7a short form
b present in the depression 4a, 6a, 8a and 8b short form
c present in the depression 6a, 8a and 8b short form
d Based on 4047 CAT-based assessments for anxiety and 4293 CAT-based assessments for depression