Table 2.
Results of the model-comparison approach using the generalized matching equation (Eq. 1). The seven models that resulted in the lowest AICc are shown. The free parameters sM and sD were allowed to vary across all exposure groups (“vary”), vary for one exposure group (e.g., “0.3 ppm”), or remain constant across all exposure groups (“constant”). The best model is bolded.
| Model | RSS | k | n | AICc | Δ AICc | wi |
|---|---|---|---|---|---|---|
| 1. sM (vary), sD (0.3 ppm) | 1.99 | 61 | 216 | −841.52 | 0.00 | 0.84 |
| 2. sM (3.0 ppm), sD (0 ppm) | 2.49 | 49 | 216 | −836.42 | 5.10 | 0.07 |
| 3. sM (vary), sD (vary) | 1.61 | 73 | 216 | −836.18 | 5.34 | 0.06 |
| 4. sM (3.0 ppm), sD (vary) | 2.06 | 61 | 216 | −834.11 | 7.41 | 0.02 |
| 5. sM (vary), sD (3.0 ppm) | 2.07 | 61 | 216 | −833.18 | 8.35 | 0.01 |
| 6. sM (vary), sD (constant) | 2.61 | 49 | 216 | −826.09 | 15.43 | ≈ 0 |
| 7. sM (3.0 ppm), sD (3.0 ppm) | 2.65 | 49 | 216 | −822.86 | 18.67 | ≈ 0 |
RSS = residual sum of squares; k = number of parameters; n = number of data points; AICc = corrected Akaike Information Criterion; Δ AICc = difference between a model's AICc and the smallest AICc, which would be the best model tested; wi = probability that the ith model is the best model given the data.