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Absolute Risk Reduction Formula:
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Absolute Risk Reduction (ARR) is the difference in event rates between control and experimental groups in clinical trials. It measures the absolute difference in risk and is crucial for understanding the actual clinical benefit of an intervention.
The calculator uses the ARR formula:
Where:
Explanation: ARR represents the absolute difference in event rates between the control group and the treatment group, providing a clear measure of the intervention's effectiveness.
Details: ARR is essential for clinical decision-making, calculating Number Needed to Treat (NNT), and understanding the real-world impact of medical interventions. It provides a more intuitive understanding of treatment benefits than relative risk measures.
Tips: Enter both CER and EER as proportions (values between 0 and 1). For example, 0.15 represents 15% event rate. Ensure CER is greater than or equal to EER for meaningful results.
Q1: What is the difference between ARR and RRR?
A: ARR shows the absolute difference in risk, while RRR (Relative Risk Reduction) shows the percentage 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 does a negative ARR indicate?
A: A negative ARR suggests the experimental treatment may be harmful, as the event rate is higher in the treatment group than the control group.
Q4: When is ARR most useful?
A: ARR is particularly valuable when baseline risks are high and when communicating risk information to patients and clinicians.
Q5: What are the limitations of ARR?
A: ARR can be influenced by baseline risk levels and may not fully capture the clinical importance of risk reductions in different contexts.