1. What is Absolute Risk Reduction?

Absolute Risk Reduction (ARR) is the difference in risk between the control group and the experimental group in a clinical trial. It represents the absolute difference in event rates and provides a clear measure of treatment effect.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

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

Explanation: ARR measures the actual reduction in risk attributable to the intervention, expressed as an absolute difference between control and experimental groups.

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 decisions about therapeutic interventions.

4. Using the Calculator

Tips: Enter both CER and EER as fractions between 0 and 1. For example, 0.15 represents 15% event rate. Values must be valid fractions within the 0-1 range.

5. Frequently Asked Questions (FAQ)

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

Q2: How is ARR related to NNT?
A: Number Needed to Treat (NNT) is calculated as 1/ARR. It represents the number of patients needed to treat to prevent one additional adverse event.

Q3: When is ARR more useful than RRR?
A: ARR is more clinically meaningful when baseline risks are low, as RRR can exaggerate small absolute benefits.

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. Values of 0.01-0.10 are common, with higher values indicating more effective interventions.