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 of an outcome between two treatment groups.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

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

Explanation: ARR measures the actual reduction in risk attributable to the intervention, expressed as an absolute difference.

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 about intervention benefits.

4. Using the Calculator

Tips: Enter both CER and EER as proportions (values between 0 and 1). For example, 0.15 represents 15% event rate. Values must be valid proportions between 0 and 1.

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 outcome. Larger ARR values indicate greater treatment benefit.

Q4: Can ARR be negative?
A: Yes, negative ARR indicates the experimental treatment has higher risk than control (harm rather than benefit).

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