Summary of statistical models.
| Model | Fixed effects | Estimate | SE | t | p |
|---|---|---|---|---|---|
| Non-traumatic injuriesLog likelihood = –624.1 | Intercept | 7.56 | 0.59 | 12.79 | < 0.001* |
| Year | –0.27 | 0.01 | –19.22 | < 0.001* | |
| UE | 3.81 | 0.63 | 6.06 | < 0.001* | |
| Year × UE | –0.05 | 0.02 | –2.48 | 0.0136* | |
| Sprains and strainsLog likelihood = –841.9 | Intercept | 27.04 | 1.27 | 21.29 | < 0.001* |
| Year | –0.52 | 0.02 | –20.97 | < 0.001* | |
| UE | –11.6 | 0.9 | –12.96 | < 0.001* | |
| Year × UE | 0.4 | 0.03 | 11.57 | < 0.001* | |
| Traumatic injuriesLog likelihood = –876.5 | Intercept | 12.58 | 1.84 | 6.85 | < 0.001* |
| Year | –0.25 | 0.03 | –9.22 | < 0.001* | |
| UE | –1.31 | 0.89 | –1.48 | 0.1625 | |
| Year × UE | 0.08 | 0.04 | 2.19 | 0.0295* | |
| Total injuriesLog likelihood = –762.7 | Intercept | 31.52 | 1.25 | 25.3 | < 0.001* |
| Year | –0.61 | 0.02 | –29.8 | < 0.001* | |
| UE | –8.7 | 0.52 | –16.79 | < 0.001* | |
| Year × UE | 0.28 | 0.03 | 9.77 | < 0.001* |
Fixed effects, estimates, standard errors (SE), t-statistics, and p-values from all mixed-effects models analyzing the main effect of year, body part [low back versus upper extremity (UE)], and interaction effect of year and body part on normalized injury claims for each injury grouping (non-traumatic injuries, sprains and strains, traumatic injuries, and total injuries). Significant p-values (p < 0.05) are denoted by an asterisk (*). Please note that the fixed effects estimates are based on square root transformed data.