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 represents the absolute difference in risk and is a key measure of treatment effect.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

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

Explanation: ARR measures the absolute difference in event rates, providing a clear understanding of the treatment's actual benefit.

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 medical decisions.

4. Using the Calculator

Tips: Enter both CER and EER as decimal values between 0 and 1. For example, 10% should be entered as 0.10.

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 proportional reduction relative to control group risk.

Q2: How is ARR related to NNT?
A: Number Needed to Treat (NNT) = 1/ARR. It represents how many patients need treatment to prevent one additional bad outcome.

Q3: What is a clinically significant ARR?
A: Clinical significance depends on the condition and treatment. Generally, larger ARR values indicate greater treatment benefit.

Q4: Can ARR be negative?
A: Yes, negative ARR indicates the experimental treatment has higher event rates than control (harmful effect).

Q5: When should ARR be used instead of RRR?
A: ARR is preferred for clinical decision-making as it provides the actual risk difference, while RRR can be misleading when control event rates are low.