## Frequently Asked Questions

Calculating ARR is essential for understanding the effectiveness of a treatment or intervention. It quantifies the reduction in risk for a particular event between a control group and a treated group. This information can help healthcare providers and patients make informed decisions about the best course of action for prevention or treatment.

Absolute Risk Reduction (ARR) is the absolute difference between the control event rate and the experimental event rate, while Relative Risk Reduction (RRR) is the proportional reduction in the event rates between the control and experimental groups. RRR is often used to compare the effectiveness of treatments, while ARR provides a more direct measure of the actual reduction in risk.

The Number Needed to Treat (NNT) is the inverse of the Absolute Risk Reduction (ARR). To calculate NNT, simply divide 1 by ARR (expressed as a decimal). NNT represents the number of people who need to receive a treatment or intervention to prevent one event from occurring.

Yes, Absolute Risk Reduction can be negative when the experimental event rate is higher than the control event rate. A negative ARR indicates that the treatment or intervention under study is associated with an increased risk of the event occurring, rather than a reduction in risk.

Several factors can affect the calculation of Absolute Risk Reduction, including the accuracy of event rates, sample sizes, and study design. Properly conducted studies with adequate sample sizes and appropriate control groups are essential for obtaining reliable and valid ARR calculations.

Enter the control event rate and the experimental event rate into the calculator to determine the absolute risk reduction.

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- Number Needed to Treat Calculator (NNT)
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## Absolute Risk Reduction Formula

The following equation is used to calculate an absolute risk reduction.

ARR = CER - EER

- Where ARR is the absolute risk reduction (%)
- CER is the control event rate (%)
- EER is the experimental event rate (%)

## Absolute Risk Reduction Definition

An absolute risk reduction is defined as the difference between the percentage rate of a control event and an experimental rate.

## Absolute Risk Reduction Example

How to calculate absolute risk reduction?

**First, determine the control rate.**Calculate the percentage rate of the control event rate.

**Next, determine the experimental event rate.**Calculate the experimental event rate.

**Finally, calculate the absolute risk reduction.**Calculate the absolute risk reduction using the formula above.

**What is an absolute risk reduction?**

An absolute risk reduction, or ARR for short, is a measure of the absolute difference between a control group and a group receiving a treatment to prevent the event from happening.

**What is an absolute risk?**

Absolute risk is a ratio of the number of people that have a particular event, typically a medical event, compared to the total number of people that it could happen to.