Calculator Input
Enter confusion matrix values for a chemistry test, assay, or screening method. Results appear above this form after submission.
Example Data Table
These sample chemistry screening results show how confusion matrix counts influence sensitivity, specificity, and accuracy.
| Assay | True Positive | False Positive | True Negative | False Negative | Sensitivity | Specificity | Accuracy |
|---|---|---|---|---|---|---|---|
| Assay A | 88 | 12 | 146 | 14 | 86.27% | 92.41% | 90.00% |
| Assay B | 74 | 18 | 152 | 16 | 82.22% | 89.41% | 86.92% |
| Assay C | 95 | 9 | 171 | 11 | 89.62% | 95.00% | 93.01% |
Formula Used
Core Measures
Sensitivity = TP / (TP + FN)
Specificity = TN / (TN + FP)
Accuracy = (TP + TN) / Total
Predictive Values
PPV = TP / (TP + FP)
NPV = TN / (TN + FN)
Prevalence = (TP + FN) / Total
Additional Metrics
FPR = FP / (FP + TN)
FNR = FN / (TP + FN)
Balanced Accuracy = (Sensitivity + Specificity) / 2
F1 Score = 2TP / (2TP + FP + FN)
LR+ = Sensitivity / (1 - Specificity)
LR- = (1 - Sensitivity) / Specificity
How to Use This Calculator
- Enter a chemistry test or assay name.
- Fill in true positive, false positive, true negative, and false negative counts.
- Choose how many decimal places you want in the final output.
- Click Calculate Metrics to display the result section above the form.
- Review the metric cards, confusion matrix, and Plotly graph.
- Use the export buttons to save the results as CSV or PDF.
- Compare multiple assays by changing the matrix values and recalculating.
Frequently Asked Questions
1. What does sensitivity measure?
Sensitivity shows how well a chemistry test finds actual positives. A higher value means the method misses fewer positive samples and produces fewer false negatives.
2. What does specificity measure?
Specificity shows how well a test identifies actual negatives. A higher specificity means fewer false positives and better exclusion of samples that should be negative.
3. Why are false positives important?
False positives can trigger unnecessary follow-up work, repeat testing, and incorrect interpretation. In chemistry screening, they may also increase cost and reduce confidence in the assay.
4. Can this calculator be used for chemistry laboratories?
Yes. It is useful for chemistry assays, screening panels, analytical classifications, and validation studies where outcomes can be summarized as positive or negative decisions.
5. Why are PPV and NPV included?
PPV and NPV add practical meaning. They show how trustworthy positive and negative test outcomes are after considering the entered matrix counts.
6. What happens when a denominator becomes zero?
If a formula cannot be computed because its denominator is zero, the calculator returns N/A. This prevents misleading outputs and signals incomplete matrix structure.
7. Should one metric be used alone?
No. Sensitivity, specificity, predictive values, and likelihood ratios should be reviewed together. One metric alone may hide weakness in another part of assay performance.
8. What do the CSV and PDF exports save?
The exports save the test name and calculated performance metrics. This helps with reports, documentation, validation summaries, and team review.