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 benefit or harm of an intervention compared to control.

2. How Does The Calculator Work?

The calculator uses the ARR formula:

Where:

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

Example: CER = 0.20 (20%), EER = 0.10 (10%), ARR = 0.20 - 0.10 = 0.10 (10%)

3. Importance Of ARR Calculation

Details: ARR provides a clear measure of treatment effect magnitude, helping clinicians and patients understand the actual benefit of an intervention in absolute terms.

4. Using The Calculator

Tips: Enter CER and EER as fractions (e.g., 0.20 for 20%). Values must be between 0 and 1. The calculator will compute ARR and display it as both fraction and percentage.

5. Frequently Asked Questions (FAQ)

Q1: What Is The Difference Between ARR And RRR?
A: ARR shows absolute difference in risk, while RRR (Relative Risk Reduction) shows the proportional reduction in risk relative to control.

Q2: When Is ARR Most Useful?
A: ARR is most useful for understanding the actual clinical impact of a treatment and for calculating Number Needed to Treat (NNT).

Q3: How Do I Convert Percentage To Fraction?
A: Divide the percentage by 100. For example, 20% becomes 0.20, 15% becomes 0.15.

Q4: What Does A Negative ARR Mean?
A: A negative ARR indicates that the experimental treatment increases risk compared to control (absolute risk increase).

Q5: How Is ARR Related To NNT?
A: Number Needed to Treat (NNT) = 1 / ARR. For example, ARR of 0.10 gives NNT of 10.