Template:DiagnosticTesting Example
| Patients with bowel cancer (as confirmed on endoscopy) | ||||||
| Condition positive | Condition negative | Prevalence = (TP + FN) / total_population
= (20 + 10) / 2030 ≈ 1.48% |
Accuracy (ACC) = (TP + TN) / total_population
= (20 + 1820) / 2030 ≈ 90.64% | |||
| Fecal occult blood screen test outcome |
Test outcome positive |
True positive (TP) = 20 (2030 × 1.48% × 67%) |
False positive (FP) = 180 (2030 × (100% − 1.48%) × (100% − 91%)) |
Positive predictive value (PPV), precision = TP / (TP + FP)
= 20 / (20 + 180) = 10% |
False discovery rate (FDR) = FP / (TP + FP)
= 180 / (20 + 180) = 90.0% | |
| Test outcome negative |
False negative (FN) = 10 (2030 × 1.48% × (100% − 67%)) |
True negative (TN) = 1820 (2030 × (100% − 1.48%) × 91%) |
False omission rate (FOR) = FN / (FN + TN)
= 10 / (10 + 1820) ≈ 0.55% |
Negative predictive value (NPV) = TN / (FN + TN)
= 1820 / (10 + 1820) ≈ 99.45% | ||
| TPR, recall, sensitivity = TP / (TP + FN)
= 20 / (20 + 10) ≈ 66.7% |
False positive rate (FPR), fall-out, probability of false alarm = FP / (FP + TN)
= 180 / (180 + 1820) = 9.0% |
Positive likelihood ratio (LR+) = TPR/FPR
= (20 / 30) / (180 / 2000) ≈ 7.41 |
Diagnostic odds ratio (DOR) = LR+/LR−
≈ 20.2 |
F1 score = 2 × precision × recall/precision + recall
≈ 0.174 | ||
| False negative rate (FNR), miss rate = FN / (TP + FN)
= 10 / (20 + 10) ≈ 33.3% |
Specificity, selectivity, true negative rate (TNR) = TN / (FP + TN)
= 1820 / (180 + 1820) = 91% |
Negative likelihood ratio (LR−) = FNR/TNR
= (10 / 30) / (1820 / 2000) ≈ 0.366 | ||||