1. What is Risk Difference?

Risk Difference (RD) is the absolute difference in event rates between two groups. It's calculated by subtracting the Control Event Rate (CER) from the Experimental Event Rate (EER). It provides a direct measure of the absolute effect size.

2. How Does the Calculator Work?

The calculator uses the Risk Difference formula:

Where:

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

Explanation: The formula shows the absolute difference in event rates between the experimental and control groups.

3. Importance of Risk Difference

Details: Risk Difference is crucial for understanding the absolute effect of an intervention. Unlike relative measures, RD shows the actual difference in outcomes that might be expected in clinical practice.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: How does Risk Difference differ from Relative Risk?
A: RD shows absolute difference while Relative Risk shows the ratio. RD is often more clinically meaningful for understanding actual impact.

Q2: What does a negative Risk Difference mean?
A: A negative RD indicates the experimental treatment had fewer events than the control (beneficial if event is bad).

Q3: When is Risk Difference most useful?
A: RD is particularly valuable when the baseline risk is high and you want to understand the absolute impact of an intervention.

Q4: What are the limitations of Risk Difference?
A: RD doesn't account for baseline risk differences between populations and may be harder to compare across studies with different baseline risks.

Q5: How should I interpret a Risk Difference of 5%?
A: This means 5 more (or fewer) events per 100 patients in the experimental group compared to control.