Ranges of DBH, tree health variables, and stress index for all city-owned ash trees and the validation data set re-measured by a tree health assessment expert. Expert versus volunteer mean differences and Wilcoxon P-values. Bolded P-values indicate where expert and volunteer ratings were significantly different (P < 0.05) from each other.
| Variable | All trees | Validation data | Expert versus volunteer | |||
|---|---|---|---|---|---|---|
| (n = 316) | (n = 64) | Mean | Wilcoxon | |||
| min | max | min | max | diff. | P | |
| DBH (cm) | 12 | 124 | 14 | 124 | 0.05 | <0.0001 |
| Defoliation | 1 | 3 | 1 | 2 | −0.46 | <0.0001 |
| Discoloration | 1 | 5 | 1 | 3 | 0.10 | 0.809 |
| Dieback | 1% | 80% | 1% | 80% | 3% | 0.0304 |
| Transparency | 6% | 62% | 6% | 61% | 5% | 0.0001 |
| Vigor | 1 | 5 | 1 | 5 | 0.12 | 0.2489 |
| Stress index | 0.00 | 3.70 | 0.00 | 3.50 | 0.02 | 0.638 |