| Coefficient of correlation | Correlation |
| 0.0 - ±0.2 | Little correlation |
| ±0.2 - ±0.4 | Weak correlation |
| ±0.4 - ±0.7 | Correlated |
| ±0.7 - ±0.9 | Strong correlation |
| ±0.9 - ±1.0 | Very strong correlation |