Fig. 5

Univariate regression and multivariate regression. A The linear relationships between the predictors and Joint Gap. Residual and fitting values (B, upper left). Data points between residual and fitting values were evenly distributed on both sides of y = 0, showing a random distribution, and the red line presented a smooth curve. Residual Q-Q chart (B, upper right), data points were distributed diagonally in a straight line, conforming to normal distribution. Normalized residual square root and fitting value (B, bottom left), data points were evenly distributed on both sides of y = 0, showing a random distribution. Standardized residuals and leverage values (B, bottom right), with no outliers that affected the regression model