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

3. Interpretation of Results

Details:

• RR = 1: No difference in risk between groups
• RR > 1: The treatment/exposure increases risk
• RR < 1: The treatment/exposure decreases risk (protective effect)
• The further from 1, the stronger the association

4. Using the Calculator

Tips: Enter the number of events and total participants for both treatment and control groups. All values must be non-negative integers, and event counts cannot exceed group totals.

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: When is relative risk most appropriate?
A: RR is ideal for cohort studies and randomized controlled trials where you can measure incidence.

Q3: How precise is the RR calculation?
A: The point estimate alone doesn't show precision. Confidence intervals are needed for complete interpretation.

Q4: Can RR be greater than 1 even if not statistically significant?
A: Yes, the point estimate may suggest increased risk, but without statistical significance, we can't be confident it's not due to chance.

Q5: What are limitations of relative risk?
A: RR doesn't account for confounding variables and can be misleading with rare outcomes or small sample sizes.