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 between two treatment options.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

• \( CER \) — Control Event Rate (proportion)
• \( EER \) — Experimental Event Rate (proportion)

Explanation: The formula calculates the absolute difference in event rates between control and experimental groups, multiplied by 100 to express as percentage.

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 proportions (values between 0 and 1). For example, if 20% of patients experienced an event, enter 0.20.

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 the proportional reduction in risk relative to control group.

Q2: How is ARR related to NNT?
A: Number Needed to Treat (NNT) = 1/ARR. It represents how many patients need to be treated 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 more effective treatments.

Q4: Can ARR be negative?
A: Yes, negative ARR indicates the experimental treatment is worse than control, which would be Absolute Risk Increase (ARI).

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 with small baseline risks.