Table 2.
Generalized linear model testing the effects of sampling year (1993–2012), ecological zone (zones 1 and 2) and their interaction on bioassay mortality for (a) DDT, (b) permethrin, (c) deltamethrin, (d) carbamates (bendiocarb & propoxur), (e) organophosphates (fenitrothion & malathion)
| (a) DDT | Wald χ 2 | d.f. | P-value |
|---|---|---|---|
| Intercept | 337.471 | 1 | 0.000 |
| Year (covariate) | 337.866 | 1 | 0.000 |
| Ecological zone | 68.178 | 1 | 0.000 |
| Year × ecological zone | 68.062 | 1 | 0.000 |
| (b) deltamethrin | Wald χ 2 | d.f. | P-value |
| Intercept | 56.854 | 1 | 0.000 |
| Year (covariate) | 55.615 | 1 | 0.000 |
| Ecological zone | 4.833 | 1 | 0.028 |
| Year × ecological zone | 4.926 | 1 | 0.026 |
| (c) permethrin | Wald χ 2 | d.f. | P-value |
| Intercept | 6.848 | 1 | 0.009 |
| Year (covariate) | 7.001 | 1 | 0.008 |
| Insecticide concentration | 63.232 | 1 | 0.000 |
| Ecological zone | 33.974 | 1 | 0.000 |
| Year × ecological zone | 33.889 | 1 | 0.000 |
| (d) carbamate | Wald χ 2 | d.f. | P-value |
| Intercept | 1.205 | 1 | 0.272 |
| Year (covariate) | 1.193 | 1 | 0.275 |
| Insecticide type | 5.922 | 1 | 0.015 |
| Ecological zone | 72.697 | 1 | 0.000 |
| Year × ecological zone | 72.311 | 1 | 0.000 |
| (e) organophosphate | Wald χ 2 | d.f. | P-value |
| Intercept | 1.517 | 1 | 0.218 |
| Year (covariate) | 1.693 | 1 | 0.193 |
| Ecological zone | 59.664 | 1 | 0.000 |
| Year × ecological zone | 59.063 | 1 | 0.000 |
In (b) and (c) two (similar) insecticide concentrations were present in the data so this term was also included as an effect in each model but not in interactions owing to insufficient variance.