Table 1.
The 3-CPL model is selected as the best, since it has the lowest BIC (italics). As the number of parameters in the model increases, the likelihood of the model given the data increases. However, the BIC shows that this improvement is only justified up to the 3-CPL model, after which the more complex models are overfit to the data.
| model | parameters | maximum log likelihood | BIC |
|---|---|---|---|
| uniform | 0 | −9976.29 | 19952.58 |
| 1-CPL | 1 | −9862.86 | 19732.90 |
| 2-CPL | 3 | −9833.87 | 19689.26 |
| 3-CPL | 5 | −9792.05 | 19619.97 |
| 4-CPL | 7 | −9790.87 | 19631.97 |
| 5-CPL | 9 | −9790.40 | 19645.38 |