Fig. 3

ROC curves in predicting erectile function by free testosterone value (a predicting IIEF-5 over 17 points, AUC = 0.634; b predicting IIEF-5 over 12 points, AUC = 0.782). ROC = receiver operating characteristic; AUC = area under curve

Note: since higher free testosterone value was related to better erectile function, the ROC curves are showing the prediction of having the ability for sexual life, NOT the occurrence of ED.