| 76 | |
| 77 | |
| 78 | class vf(sm.families.varfuncs.VarianceFunction): |
| 79 | def __call__(self, mu): |
| 80 | return mu**2 * (1 - mu)**2 |
| 81 | |
| 82 | def deriv(self, mu): |
| 83 | return 2 * mu - 6 * mu**2 + 4 * mu**3 |
| 84 | |
| 85 | |
| 86 | # Fit the quasi-binomial regression with the alternative variance |