🩺 Sensitivity and Specificity Calculator
Calculate sensitivity, specificity, positive predictive value, negative predictive value, and accuracy.
📊 Statistics📐 Formula included🧠 Practice questions✓ Free
Please enter valid values.
Formula and Explanation
Calculate sensitivity, specificity, positive predictive value, negative predictive value, and accuracy.
| Concept | Formula or rule |
|---|---|
| Sensitivity and Specificity Calculator | Sensitivity=TP/(TP+FN) · Specificity=TN/(TN+FP) |
How to Use This Calculator
- Enter the sample, counts, probabilities, or summary statistics requested above.
- Keep paired lists in the same order and separate values with commas.
- Select the correct test direction or sample/population option when available.
- Press Calculate and interpret the result together with the supporting statistics.
Worked Example
Example: TP=80 and FN=20 gives sensitivity 80%. TN=180 and FP=20 gives specificity 90%.
✓ Sensitivity 80% · Specificity 90%
Where This Is Used
School & coursework
Check homework, understand formulas, and verify step-by-step statistics exercises.
Research
Explore estimates, uncertainty, distributions, and relationships before using full statistical software.
Business & data analysis
Summarize variation, compare groups, and communicate data-driven findings clearly.
Common Mistakes to Avoid
⚠️
Confusing sensitivity with PPV
PPV depends strongly on prevalence.
PPV depends strongly on prevalence.
⚠️
Ignoring the decision threshold
Changing a test threshold trades sensitivity against specificity.
Changing a test threshold trades sensitivity against specificity.
⚠️
Evaluating on a biased sample
Performance may not generalize to the target population.
Performance may not generalize to the target population.
Practice Questions
1. TP=90, FN=10. Find sensitivity.
Answer: 90%
2. TN=80, FP=20. Find specificity.
Answer: 80%
3. Which metric answers ‘among positive tests, how many are truly positive’?
Answer: PPV.
Frequently Asked Questions
What does sensitivity measure?▾
The share of truly positive cases correctly identified.
What does specificity measure?▾
The share of truly negative cases correctly identified.
Why does PPV change with prevalence?▾
The mix of positive and negative cases affects the proportion of positive results that are true.