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Absolute Risk Reduction Formula:
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Absolute Risk Reduction (ARR) is the difference in event rates between the control group and the experimental group in a clinical trial. It represents the absolute difference in risk between the two groups and is a key measure of treatment effect.
The calculator uses the ARR formula:
Where:
Explanation: ARR measures the absolute difference in event rates between the control and experimental groups, providing a clear picture of the treatment'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 treatment benefits versus risks.
Tips: Enter both CER and EER as fractions (values between 0 and 1). For example, if 20% of patients experienced an event, enter 0.20.
Q1: What is the difference between ARR and RRR?
A: ARR shows the absolute difference in risk, while Relative Risk Reduction (RRR) shows the proportional reduction in risk relative to the control group.
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 adverse event.
Q3: What is a clinically significant ARR?
A: Clinical significance depends on the context - the disease severity, treatment risks, and patient preferences. Generally, larger ARR values indicate greater treatment benefit.
Q4: Can ARR be negative?
A: Yes, a negative ARR indicates that the experimental treatment has a higher event rate than the control, suggesting potential harm.
Q5: When should ARR be used instead of RRR?
A: ARR is generally preferred for clinical decision-making as it provides the absolute magnitude of benefit, while RRR can be misleading when control event rates are low.