1. What is Relative Risk?

Relative Risk (RR) is a measure of the strength of association between an exposure and an outcome. It compares the probability of an event occurring in the exposed group versus the control group.

2. How Does the Calculator Work?

The calculator uses the Relative Risk formula:

Where:

• \( EER \) — Experimental Event Rate (events in treatment group)
• \( CER \) — Control Event Rate (events in control group)

Explanation: RR = 1 means no difference between groups. RR > 1 means increased risk in exposed group. RR < 1 means decreased risk in exposed group.

3. Interpreting Relative Risk

Details:

• RR = 1: No association between exposure and outcome
• RR > 1: Positive association (increased risk)
• RR < 1: Negative association (protective effect)

4. Using the Calculator

Tips: Enter both EER and CER as percentages (0-100%). CER must be greater than 0. Results are dimensionless.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between RR and OR?
A: Relative Risk compares probabilities directly, while Odds Ratio compares odds. RR is more intuitive but can't be used in case-control studies.

Q2: When should I use Relative Risk?
A: RR is ideal for cohort studies and clinical trials where you can calculate actual probabilities of events.

Q3: What's considered a "significant" RR value?
A: Depends on context, but typically RR < 0.5 or > 2.0 are considered clinically significant, though statistical significance depends on confidence intervals.

Q4: How do I convert percentages to rates?
A: Simply divide by 100. For example, 25% = 0.25 rate.

Q5: Can RR be negative?
A: No, RR ranges from 0 to infinity. Values between 0-1 indicate reduced risk, values >1 indicate increased risk.