Table 4.
Key statistics from the cluster analyses of residuals from the logistic regression model with x- and y-coordinates as the only predictors, and the final logistic regression model with all risk factors included, for BRSV and BCoV antibodies in bulk tank milk in 1194 dairy herds in two counties on the northwest coast of Norway. “Mean inside” and “Mean outside” refers to the mean value of deviance residuals inside and outside the cluster, respectively.
| Number of cases | Mean inside | Mean outside | Standard dev. | Log-likelihood ratio | p-value | |
|---|---|---|---|---|---|---|
| BRSV xy-model: | ||||||
| 1. cluster | 180 | 0.66 | −0.15 | 1.11 | 39.92 | 0.001 |
| 2. cluster | 41 | 1.21 | −0.072 | 1.12 | 25.08 | 0.001 |
| 3. cluster | 31 | 1.08 | −0.057 | 1.13 | 15.13 | 0.001 |
| 4. cluster | 16 | 1.38 | −0.047 | 1.14 | 12.30 | 0.005 |
| 5. cluster | 10 | 1.55 | −0.041 | 1.14 | 9.64 | 0.040 |
| 6. cluster | 30 | 0.86 | −0.051 | 1.14 | 9.38 | 0.044 |
| BRSV final model: | ||||||
| 1. cluster | 180 | 0.58 | −0.13 | 1.06 | 33.32 | 0.001 |
| 2. cluster | 41 | 0.90 | −0.060 | 1.08 | 15.51 | 0.001 |
| 3. cluster | 31 | 0.96 | −0.053 | 1.17 | 13.22 | 0.003 |
| 4. cluster | 16 | 1.25 | −0.044 | 1.08 | 11.27 | 0.009 |
| BCoV xy-model: | ||||||
| 1. cluster | 160 | 0.64 | 0.047 | 1.03 | 22.15 | 0.001 |
| 2. cluster | 52 | 0.86 | 0.092 | 1.04 | 13.52 | 0.001 |
| 3. cluster | 233 | 0.43 | 0.052 | 1.04 | 12.47 | 0.001 |
| 4. cluster | 72 | 0.69 | 0.090 | 1.04 | 11.31 | 0.003 |
| BCoV final model*: | ||||||
| 1. cluster | 72 | 0.69 | 0.067 | 0.96 | 13.86 | 0.001 |
| 2. cluster | 37 | 0.88 | 0.080 | 0.96 | 12.46 | 0.001 |
| 3. cluster | 122 | 0.50 | 0.060 | 0.96 | 11.44 | 0.003 |
| 4. cluster | 233 | 0.34 | 0.048 | 0.96 | 8.32 | 0.027 |
*
Note that for BCoV the order of the clusters are not the same from the two models because of change in log-likelihood ratio. The 1. cluster from the final model is equivalent (regarding location) to the 4. cluster from the xy-model.