Table 3.
Item Parameters and values for the SS X2 Fit Index and LR DIF Statistics for the Anger Items
| Item Stem | Item Parameters | S-X2 Fit Index | DIF between boys and girls | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| a | b1 | b2 | b3 | b4 | X2 | d.f. | p | X2 | d.f. | p | |
| I felt mad. | 2.15 | −1.54 | −0.47 | 1.56 | 2.56 | 41 | 29 | .076 | 4.0 | 5 | 0.549 |
| I was so angry I felt like yelling at somebody. | 1.97 | −0.47 | 0.41 | 1.51 | 2.16 | 52 | 33 | .019 | 1.1 | 5 | 0.954 |
| I was so angry I felt like throwing something. | 1.82 | 0.20 | 0.98 | 2.14 | 2.75 | 54 | 30 | .005 | 15.0 | 5 | 0.010 |
| When I got mad, I stayed mad. | 1.55 | 0.01 | 1.04 | 2.33 | 3.30 | 52 | 31 | .010 | 2.7 | 5 | 0.746 |
| I felt upset. | 1.53 | −1.41 | −0.24 | 1.58 | 2.66 | 63 | 32 | .001 | 23.0 | 5 | 0.000 |
| I felt fed up.† | 1.31 | −0.54 | 0.41 | 2.07 | 3.54 | 51 | 35 | .036 | 5.3 | 5 | 0.380 |
| Items set aside due to LD: | |||||||||||
| I felt angry. | 1.72 | −1.13 | 0.04 | 1.83 | 3.07 | 34 | 32 | 0.370 | 9.3 | 5 | 0.098 |
| I was so angry I acted grouchy towards other people. | 1.73 | −0.61 | 0.14 | 1.42 | 2.39 | 46 | 34 | 0.081 | 8.9 | 5 | 0.113 |
| I was so angry I felt like hitting something. | 1.51 | 0.20 | 1.00 | 2.06 | 3.00 | 31 | 31 | 0.457 | 22.0 | 5 | 0.001 |
The scale for the item parameters is set such that the distribution of depressive symptoms in the reference population (represented by the NC portion of the sample) is standardized, mean 0 variance 1, as is conventional for reporting IRT parameters.
†
In the analysis of DIF by age (8–12 and 13–17 years old), only “I felt fed up” exhibited significant DIF after the Benjamini-Hochberg correction.