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 reduced risk in treatment group.

3. Interpretation of Results

Details:

• RR = 1: No difference in risk between groups
• RR > 1: Increased risk in treatment group
• RR < 1: Reduced risk in treatment group (protective effect)

4. Using the Calculator

Tips: Enter the number of events and total subjects for both treatment and control groups. All values must be non-negative integers.

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 relative risk?
A: Precision depends on sample size. Larger studies provide more reliable RR estimates.

Q4: Should I report confidence intervals with RR?
A: Yes, always report 95% confidence intervals to show the precision of your RR estimate.

Q5: What are limitations of relative risk?
A: RR doesn't convey absolute risk differences and can be misleading when event rates are very low or very high.