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Absolute Risk Reduction Formula:
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Absolute Risk Reduction (ARR) is the absolute difference in event rates between control and experimental groups in clinical studies. It represents the actual reduction in risk attributable to the intervention being studied.
The calculator uses the ARR formula:
Where:
Explanation: ARR measures the actual difference in event rates between the control group and the treatment group, providing a clear picture of the intervention's effectiveness.
Details: ARR is crucial for understanding the clinical significance of treatment effects, calculating Number Needed to Treat (NNT), and making informed decisions about therapeutic interventions.
Tips: Enter both CER and EER as proportions (values between 0 and 1). For example, enter 0.15 for 15% event rate. All values must be valid proportions.
Q1: What is the difference between ARR and RRR?
A: ARR shows the absolute difference in event rates, while RRR (Relative Risk Reduction) shows the proportional reduction relative to the control group rate.
Q2: How is ARR related to NNT?
A: Number Needed to Treat (NNT) is calculated as 1/ARR. It represents the number of patients needed to treat to prevent one additional bad outcome.
Q3: When is ARR more useful than RRR?
A: ARR is more clinically meaningful because it provides the actual risk difference, while RRR can be misleading when control event rates are low.
Q4: What does a negative ARR indicate?
A: A negative ARR suggests that the experimental treatment may be harmful, as the event rate is higher in the treatment group than in the control group.
Q5: How should ARR be interpreted in clinical practice?
A: ARR should be considered alongside confidence intervals, p-values, and clinical relevance to make informed treatment decisions.