Table 1.

Imputed datasets with eight imputation methods.

Imputed Datasets	Imputation Method
Mean	filling in the mean of all non-missing observations in training set; filling in the mean of all non-missing observations in test set, separately
Normal	filling in the mean of non-SSI patients in training set; filling in the mean of non-SSI patients in test set, separately
MICE	using multivariate regression model
0	filling in 0 for all missing values
Dummy+Mean	adding dummy variables to model “mean”
Dummy+Normal	adding dummy variables to model “normal”
Dummy+MICE	adding dummy variables to model “MICE”
Dummy+0	adding dummy variables to model “0”