Table 1.
Overall fit statistics and tests of local independence by set
| Item set | 1 | 2 | 3 | 4 |
| Summary statistics | ||||
| Persons (n) | 255 | 287 | 289 | 283 |
| Mean item fit residual (SD) | 0.02 (1.83) | −0.03 (1.52) | −0.14 (1.11) | −0.08 (1.38) |
| Mean person location (SD) | −0.81 (1.00) | −1.06 (0.97) | −1.15 (0.96) | −1.15 (0.75) |
| Overall χ2 value (df) | 177.6 (75) | 194.3 (96) | 189.5 (96) | 170.7 (72) |
| χ2 probability | 0.00 | 0.00 | 0.00 | 0.00 |
| Person Separation Index | 0.75 | 0.70 | 0.69 | 0.54 |
| Cronbach’s alpha | 0.81 | 0.78 | 0.78 | 0.63 |
| Items with misfit (n) | 2 | 1 | 1 | 1 |
| Persons with misfit (n) | 0 | 2 | 1 | 3 |
| Tests for multidimensionality and response dependency | ||||
| Proportion of significant paired t-tests (%) | 3.5 | 2.8 | 2.8 | 5.7 |
| Dependent pairs of items (n) | 0 | 0 | 0 | 0 |