1. What Are Relative and Absolute Risk?

Relative Risk (RR) and Absolute Risk (AR) are fundamental epidemiological measures used to quantify the association between exposure and disease outcomes. RR compares the probability of an event occurring in exposed vs. unexposed groups, while AR measures the actual difference in risk between the two groups.

2. How Does the Calculator Work?

The calculator uses the following formulas:

Where:

• \( Event\ Rate\ Exposed \) — Proportion of events in exposed group
• \( Event\ Rate\ Unexposed \) — Proportion of events in unexposed group
• \( RR \) — Relative Risk (ratio)
• \( AR \) — Absolute Risk (proportion difference)

Explanation: RR values >1 indicate increased risk with exposure, RR=1 indicates no effect, and RR<1 indicates protective effect. AR provides the actual risk difference between groups.

3. Importance of Risk Calculations

Details: These measures are crucial for understanding the strength of association in epidemiological studies, clinical decision-making, public health interventions, and risk communication to patients.

4. Using the Calculator

Tips: Enter event rates as proportions (0 to 1). For example, if 25 out of 100 exposed individuals developed the outcome, enter 0.25. Both rates must be valid proportions, and the unexposed rate cannot be zero.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between RR and AR?
A: RR shows the relative comparison (ratio), while AR shows the absolute difference in risk. RR is better for understanding strength of association, AR for understanding public health impact.

Q2: When should I use RR vs AR?
A: Use RR for etiological research and AR for clinical decision-making and public health planning. Both provide complementary information.

Q3: What does an RR of 2.0 mean?
A: An RR of 2.0 means the exposed group has twice the risk of the outcome compared to the unexposed group.

Q4: How do I interpret negative AR values?
A: Negative AR indicates the exposure is protective - the exposed group has lower risk than the unexposed group.

Q5: What are the limitations of these measures?
A: They don't account for confounding factors, time dimensions, or competing risks. Always consider study design and potential biases.