Table 5. Results of statistical analyses of sequential operative times fitted by the non-linear least squares estimation method based on a nonlinear regression model after adjustment for confounding factors.

All the statistics were derived from the non-linear regression (phase-wise linear regression) analysis based on Equation (1) shown in the Materials and Methods section. B0, B1, B2, B3, and B4 stand for the regression parameter estimates; C1, C2, and C3 stand for the structural changing time points. R²: the coefficient of determination (Surgeon A's R²=0.460, Surgeon B's R²=0.506).