Table 4. Resource hypothesis model formulation and coefficient estimates for cross sectional prevalence study design.
Model | Parameter | Coefficient estimate | Standard error | Z value | P value | Odds ratio |
log [π÷(1−π)] = β1+β2CS+β3DS+β4 |ΔEVI|+β5HS+β6NWB+β7DW+β8DP+β9X+β10Y+r.eff.(location) Calibration: le Cessie-van Houwelingen goodness of fit test (Z = 0.2, P = 0.8) Validation: AUC 0.7 Pseudo r2 = 14% | (Intercept) | 12.04 | 143.76 | 0.08 | 0.93 | … |
Condition score (CS) | 0.76 | 0.39 | 1.93 | 0.05 | 2.13 | |
Dist. to streams (DS) | −0.57 | 0.21 | −2.73 | 0.01 | 0.57 | |
EVI decline (ΔEVI) | −0.38 | 0.15 | −2.59 | 0.01 | 0.68 * | |
Herd size (HS) | 0.01 | 0.02 | 0.61 | 0.54 | 1.01 | |
No. water bodies (NWB) | 0.06 | 0.05 | 1.26 | 0.21 | 1.06 | |
Wallaby herd density (DW) | 0.38 | 0.38 | 1.00 | 0.32 | 1.46* | |
Wild pig density (DP) | −0.84 | 0.40 | −2.09 | 0.04 | 0.43 * | |
X coordinate (X) | −0.34 | 0.90 | −0.38 | 0.71 | 0.71 | |
Y coordinate (Y) | −1.60 | 2.29 | −0.70 | 0.49 | 0.20 |
Random effects terms for herd, and fixed effect covariates for latitude and longitude were included to control clustering of data and spatial trends or autocorrelation.
These covariates were transformed (normalised z = (x−μ)÷σ) to yield more interpretable odds ratios.