Table 3.
Correlations Between Congeneric and 1PL IRT Fits, Data From 1PL IRT Model.
| Correlation in discrimination parameter |
Correlation in difficulty parameter |
Correlation in factor scores |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| 1PL data vs. congeneric fit | Minimum | Median | Maximum | Minimum | Median | Maximum | Minimum | Median | Maximum |
| Case 1 | • | • | • | 0.993 | 0.998 | 0.999 | 0.997 | 0.998 | 0.999 |
| Case 2 | • | • | • | 0.995 | 0.999 | 1.000 | 0.998 | 0.999 | 0.999 |
| Case 3 | • | • | • | 0.986 | 0.998 | 0.999 | 0.999 | 0.999 | 0.999 |
| Case 4 | • | • | • | 0.997 | 0.999 | 1.000 | 0.999 | 0.999 | 1.000 |
| Case 5 | • | • | • | 0.995 | 0.998 | 0.999 | 0.999 | 0.999 | 1.000 |
| Case 6 | • | • | • | 0.998 | 0.999 | 1.000 | 0.999 | 0.999 | 1.000 |
Note. 1PL IRT = one-parameter logistic item response theory. • = Discrimination parameter is not available in the 1PL IRT model, and loadings are not unique in the parallel model. With these models, the correlation is not calculated.