Table 2 Formulas for computation of qualitative DAMs
Measure | Formula |
|---|---|
Sensitivity or True Positive Rate (TPR) | TP / (TP + FN) |
Specificity or True Negative Rate (TNR) | TN / (TN + FP) |
Positive Predictive Values (PPV) | TP / (TP + FP) |
Negative Predictive Value (NPV) | TN / (TN + FN) |
Upward Misclassification or False Positive Rate (FPR) or Type I error | FP / (FP + TN) = 1 – Specificity |
Downward Misclassification or False Negative Rate (FNR) or Type II Error | FN / (TP + FN) = 1 – Sensitivity |
False Omission Rate (FOR) | FN / (FN + TN) = 1 - NPV |
False Discovery Rate (FDR) | FP / (TP + FP) = 1 - PPV |
Positive Likelihood Ratio (LR+) | Sensitivity / (1 – Specificity) |
Negative Likelihood Ratio (LR–) | (1 – Sensitivity) / Specificity |
Diagnostic Accuracy | (TP + TN) / (TP + FP + TN + FN) |
Disease Prevalence | (TP + FN) / (TP + FP + TN + FN) |
Diagnostic Odds Ratio (DOR) | LR+ / LR– = (TP / FN) / (FP / TN) |
Youden’s Index | Sensitivity + Specificity − 1 |
Kappa coefficient | (po – pe) / (1 – pe) where; po = (TP + TN) / (TP + FP + TN + FN) pe = ((TP + FN) * (TP + FP) + (FP + TN) * (FN + TN)) / (TP + FP + TN + FN) **2 |
F-score | 2 *(PPV * Sensitivity) / (PPV + Sensitivity) = 2 TP / (2 TP + FP + FN) |