1. What is Absolute and Relative Risk?

Absolute Risk Reduction (ARR) is the difference in event rates between control and experimental groups. Relative Risk (RR) is the ratio of event rates between experimental and control groups. These metrics are fundamental in clinical research and evidence-based medicine.

2. How Does the Calculator Work?

The calculator uses these equations:

Where:

• \( CER \) — Control Event Rate (%)
• \( EER \) — Experimental Event Rate (%)
• \( ARR \) — Absolute Risk Reduction (%)
• \( RR \) — Relative Risk (dimensionless)

Explanation: ARR shows the actual difference in risk between groups, while RR shows how much the risk changes relative to the control group.

3. Importance of Risk Calculation

Details: Understanding both absolute and relative risks is crucial for interpreting clinical trial results and making informed treatment decisions.

4. Using the Calculator

Tips: Enter both CER and EER as percentages (0-100). The calculator will compute ARR (as percentage) and RR (as ratio).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between ARR and RR?
A: ARR shows the actual difference in risk, while RR shows the proportional difference. ARR is often more clinically meaningful.

Q2: What does RR = 1 mean?
A: RR of 1 means no difference in risk between groups. RR < 1 means reduced risk, RR > 1 means increased risk.

Q3: How should I interpret ARR?
A: ARR represents the actual percentage point reduction in risk. For example, ARR of 5% means 5 fewer events per 100 patients.

Q4: When is RR more useful than ARR?
A: RR is often used when baseline risks are very low, as it can show large proportional changes that might be small in absolute terms.

Q5: What's the relationship between RR and RRR?
A: Relative Risk Reduction (RRR) is 1 - RR, expressing the reduction as a percentage of the control risk.