| Explanatory variable | Parameter estimate (B) | Student t value | Probability level of significance |
| CONSTANT | 3.861 | 18.265 | 0.000* |
| AGE | 0.011 | 342.601 | 0.000* |
| EDU | 0.001 | 0.032 | 0.974 |
| SIGMA | 0.904 | 9.818 | 0.000* |