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 experimental group versus the control group.

2. How Does the Calculator Work?

The calculator uses the Relative Risk formula:

Where:

• \( EER \) — Experimental Event Rate (percentage)
• \( CER \) — Control Event Rate (percentage)

Explanation: The formula calculates how many times more likely the event is to occur in the experimental group compared to the control group.

3. Interpretation of Relative Risk

Details:

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

4. Using the Calculator

Tips: Enter both EER and CER as percentages (0-100). The control event rate (CER) must be greater than 0.

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 is Relative Risk most useful?
A: RR is particularly useful in randomized controlled trials and cohort studies where the risk can be measured directly.

Q3: What are limitations of Relative Risk?
A: RR doesn't convey information about absolute risk differences and can be misleading when event rates are very low or very high.

Q4: How should I interpret an RR of 2.5?
A: An RR of 2.5 means the event is 2.5 times more likely in the experimental group compared to the control group.

Q5: Should I always aim for RR < 1 in medical studies?
A: It depends on the outcome being measured. For adverse outcomes, RR < 1 is desirable. For beneficial outcomes, RR > 1 may be desirable.