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RRR Calculation Formula:
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Relative Risk Reduction (RRR) is a measure that expresses the proportional reduction in risk between treatment and control groups in clinical trials. When derived from hazard ratios in survival analysis, it approximates the percentage reduction in risk associated with an intervention.
The calculator uses the simplified RRR formula:
Where:
Explanation: This approximation assumes proportional hazards and provides a quick estimate of treatment effect magnitude. The result is typically converted to percentage by multiplying by 100.
Details: RRR helps clinicians and researchers understand the magnitude of treatment benefits in relative terms, facilitating comparisons between different interventions and supporting clinical decision-making.
Tips: Enter the hazard ratio (HR) value obtained from survival analysis. Valid HR values are typically ≥0. The calculator will compute the approximate relative risk reduction as a percentage.
Q1: What is the difference between RRR and ARR?
A: RRR expresses risk reduction as a proportion of baseline risk, while Absolute Risk Reduction (ARR) shows the actual difference in risk between groups.
Q2: When is this approximation valid?
A: This approximation works best when hazard ratios are constant over time (proportional hazards assumption) and event rates are not extremely high.
Q3: What does a negative RRR indicate?
A: A negative RRR suggests increased risk in the treatment group compared to control, which may indicate harmful effects.
Q4: How should RRR be interpreted clinically?
A: RRR should be considered alongside baseline risk, as the same RRR can have different clinical importance depending on the underlying event rate.
Q5: Are there limitations to this calculation?
A: Yes, this is an approximation. For precise calculations, especially with time-varying hazards, more complex statistical methods may be required.