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 treatment group versus the control group.

2. How Does the Calculator Work?

The calculator uses the Relative Risk formula:

Where:

• \( Event_{treatment} \) — Number of events in treatment group
• \( N_{treatment} \) — Total number in treatment group
• \( Event_{control} \) — Number of events in control group
• \( N_{control} \) — Total number in control group

Explanation: RR compares the event rate in the treatment group to the event rate in the control group. An RR of 1 means no difference between groups.

3. Interpretation of Results

Details:

• RR = 1: No difference in risk between groups
• RR > 1: Increased risk in treatment group
• RR < 1: Decreased risk in treatment group

4. Using the Calculator

Tips: Enter whole numbers for all fields. Ensure the denominator (total in each group) is greater than zero.

5. Frequently Asked Questions (FAQ)

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

Q2: What is a clinically significant RR?
A: This depends on context. Generally, RR > 2 or < 0.5 are considered strong effects, but clinical importance varies by field.

Q3: When should I use RR?
A: RR is ideal for cohort studies and randomized controlled trials where you can measure incidence.

Q4: What are limitations of RR?
A: RR doesn't convey absolute risk differences and can be misleading when baseline risks are very small.

Q5: How should I report RR in a study?
A: Always report with confidence intervals (e.g., "RR 1.5 [95% CI 1.2-1.8]") to show precision of estimate.