Estimate sensitivity, specificity and positive/negative likelihood ratios from labeled validation counts without inventing undefined rates.
How to use this tool
- Choose the event or model and review the assumptions below.
- Enter the labeled inputs.
- Select Calculate and read the labeled outputs.
- Change an input and calculate again; Reset restores the example inputs.
Calculation method
Sensitivity=TP/(TP+FN). Specificity=TN/(TN+FP). LR+=sensitivity/(1−specificity); LR−=(1−sensitivity)/specificity.
Assumptions and limits
Binary observed counts with a defined reference standard and positive class. Undefined denominators remain undefined. These are sample performance estimates without confidence intervals, not individual diagnostic probabilities.
Worked example
TP 80, FN 20, TN 90 and FP 10 give sensitivity 80%, specificity 90%, LR+ 8 and LR− 2/9. These are sample validation rates, not post-test probabilities.
Worked reading and practical questions
- Sensitivity and Specificity Need a Defined Reference Standard
- Build LR Plus and LR Minus from Test Performance Rates
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Frequently asked questions
What does this calculator assume?
Binary observed counts with a defined reference standard and positive class. Undefined denominators remain undefined. These are sample performance estimates without confidence intervals, not individual diagnostic probabilities.
How do I enter and update the inputs?
Use the labeled fields, then select Calculate. Percent fields use 0 to 100. After editing, calculate again; Reset restores the example inputs.