Appendix D: Feature selection methods
PD
Method 1: The Mann‒Whitney U test was performed to investigate which features differed significantly between PD and ET, and we called this feature combination Feature Group I (FG I).Method 2: Spearman's rank correlation test was performed for every pair of the above significant features to remove features with high correlations (Set threshold Method 3: Fivefold cross-validation ROC area under the curve (AUC) of the above significant features obtained from Method 1 was computed individually. Then, considering that (1) the AUC values of our features are all lower than 0.7 and (2) AUC ≥ 0.6 represents that it has the power to be at least not fail for a diagnostic test, which we found from one previous study [