⚕️ Relative Risk Calculator
Calculate relative risk, absolute risk difference, and approximate confidence interval from a 2×2 table.
📊 Statistics📐 Formula included🧠 Practice questions✓ Free
Please enter valid values.
Formula and Explanation
Calculate relative risk, absolute risk difference, and approximate confidence interval from a 2×2 table.
| Concept | Formula or rule |
|---|---|
| Relative Risk Calculator | RR = [a/(a+b)] / [c/(c+d)] |
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: Risk exposed=30/100=0.30; risk control=15/100=0.15.
✓ RR=2.0 and risk difference=15 percentage points
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
⚠️
Using case-control data for direct risk
Case-control sampling generally supports odds ratios, not direct risks.
Case-control sampling generally supports odds ratios, not direct risks.
⚠️
Ignoring follow-up time
Different observation periods may require rates rather than risks.
Different observation periods may require rates rather than risks.
⚠️
Confusing relative and absolute effects
Both can be important.
Both can be important.
Practice Questions
1. Risk 20% vs 10%. Find RR.
Answer: 2
2. Risk 20% vs 10%. Find risk difference.
Answer: 10 percentage points
3. What does RR<1 suggest?
Answer: Lower risk in the first group.
Frequently Asked Questions
What does RR=1 mean?▾
Equal risk in both groups.
What does RR=2 mean?▾
The first group’s risk is twice the second group’s risk.
Can RR be negative?▾
No.