1. What is Absolute Risk Reduction?

Absolute Risk Reduction (ARR) is the difference in risk between the control group (CER) and the treatment group (EER). It measures how much a treatment reduces the risk of an outcome compared to a control.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

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

Explanation: ARR shows the absolute difference in event rates between two groups, providing a clear measure of treatment effect.

3. Importance of ARR Calculation

Details: ARR is crucial for understanding the clinical significance of study results. Unlike relative measures, ARR gives the actual difference in risk between groups.

4. Using the Calculator

Tips: Enter both CER and EER as percentages (0-100). The calculator will compute the absolute difference between them.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between ARR and RRR?
A: ARR shows absolute difference (CER-EER), while RRR (Relative Risk Reduction) shows proportional reduction ((CER-EER)/CER).

Q2: When is ARR most useful?
A: ARR is most valuable when assessing clinical significance, especially for common outcomes where small relative changes may represent large absolute differences.

Q3: How does ARR relate to NNT?
A: Number Needed to Treat (NNT) is the reciprocal of ARR (1/ARR). It tells how many patients need treatment to prevent one additional bad outcome.

Q4: Can ARR be negative?
A: Yes, negative ARR indicates the treatment increased risk compared to control.

Q5: What's a good ARR value?
A: Interpretation depends on context. Larger ARR values indicate more effective treatments, but clinical importance depends on the outcome being measured.