1. What is Absolute Risk Reduction?

Absolute Risk Reduction (ARR) is the difference in event rates between control and experimental groups in clinical trials. It measures the absolute difference in risk between two treatment options.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

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

Explanation: ARR represents the actual reduction in risk attributable to the experimental intervention compared to the control.

3. Importance of ARR Calculation

Details: ARR is crucial for understanding the clinical significance of treatment effects, calculating Number Needed to Treat (NNT), and making informed clinical decisions.

4. Using the Calculator

Tips: Enter both CER and EER as percentages (0-100%). Positive ARR indicates risk reduction, negative ARR indicates risk increase.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between ARR and RRR?
A: ARR shows absolute difference in risk, while Relative Risk Reduction (RRR) shows proportional reduction compared to control group risk.

Q2: How is ARR related to NNT?
A: Number Needed to Treat (NNT) = 1/ARR (when ARR is expressed as a decimal). Lower NNT indicates more effective treatment.

Q3: When is ARR more useful than RRR?
A: ARR is more clinically meaningful as it shows the actual risk difference, while RRR can be misleading when baseline risk is low.

Q4: Can ARR be negative?
A: Yes, negative ARR indicates the experimental treatment increases risk compared to control (Absolute Risk Increase).

Q5: What are typical ARR values in clinical trials?
A: ARR values vary widely by condition and treatment, ranging from <1% to >20% depending on intervention effectiveness.