Table 2 Apparent and optimism-corrected MSE values based on the four approaches (“Appr 1”, “Appr 2”, “Appr 3” and “Appr 4”) of handling multiply imputed data sets, and the shrinkage factor ( ${\bar{\beta }}_{L{P}^{\ast }}$ )

From: Validation of prediction models based on lasso regression with multiply imputed data