Table 2. Potency factors for Cr(VI) obtained using Poisson regression.
| Poisson model | Lag (years) | β (Potency factor)a | −2LL |
|---|---|---|---|
| Relative | 0 | 0.725 | 232.31 |
| Additive | 0.00118 | 230.04 | |
| Relative | 5 | 0.732 | 230.20 |
| Additive | 0.00127 | 228.17 | |
| Relative | 10 | 0.703 | 226.35 |
| Additive | 0.00135 | 224.90 | |
| Relative | 15 | 0.700 | 226.91 |
| Additive | 0.00169 | 221.68 |
Abbreviation: –2LL, negative two log-likelihood.
a
The units of β for the relative risk model are (mg/m3-years)−1, and for the additive model are (mg/m3-years per person-year)−1, β obtained with γ=0 and α=1.