1. What is Relative Risk?

Definition: Relative Risk (RR) is a measure of the strength of association between an exposure and an outcome in epidemiological studies.

Purpose: It compares the probability of an event occurring in the exposed group versus the unexposed group.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( RR \) — Relative Risk (dimensionless)
• \( I_e \) — Incidence in exposed group (dimensionless)
• \( I_u \) — Incidence in unexposed group (dimensionless)

Interpretation:

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

3. Importance of Relative Risk

Details: RR is crucial in epidemiology for assessing disease risk factors, evaluating treatment effectiveness, and making public health decisions.

4. Using the Calculator

Tips: Enter incidence rates (as proportions between 0 and 1) for both exposed and unexposed groups. The unexposed group incidence must be greater than 0.

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: How do I interpret an RR of 2.5?
A: An RR of 2.5 means the exposed group has 2.5 times the risk of the outcome compared to the unexposed group.

Q3: What's considered a "significant" RR?
A: Depends on context, but generally RR > 2 or < 0.5 are considered strong associations in epidemiology.

Q4: Can RR be negative?
A: No, RR ranges from 0 to infinity since incidence rates can't be negative.

Q5: When is RR most appropriate to use?
A: In cohort studies or randomized controlled trials where true incidence rates can be calculated.