Multiple regression analysis*
| Standard regression equation | r | R2 | Adjusted R2 | F | p value |
|---|---|---|---|---|---|
| Model 1. Procedure length = 2.8 (IDS) + 23.9 | 0.67 | 0.45 | 0.45 | 477.9 | < 0.001 |
| Model 2. Procedure length = 2.3 (IDS) + 8.1 (team) − 27.7 | 0.71 | 0.51 | 0.51 | 304.8 | < 0.001 |
| Model 3. Procedure length = 2.3 (IDS) + 7.1 (team) +7.9 (ASA) − 0.3 (age) − 20.2 | 0.72 | 0.53 | 0.52 | 160.8 | < 0.001 |
Age = patient age; ASA = American Society of Anesthesiologists; IDS = index of difficulty of surgery; team = number of team members.
↵* r denotes the correlation coefficients between the predictors and procedure length. R2 (especially the adjusted R2) is the percentage of variance in the dependent variable explained collectively by all of the independent variables. F is used to determine the significance of using the model to predict procedure length compared with a “best guess.” The p value is used to estimate the improvement of the model in predicting the change in procedure length.