# Resources

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### Glossary

• Absolute Risk Reduction (ARR): The absolute arithmetic difference in rates of bad outcomes between experimental and control participants in a trial.
• FEV1: The volume of air that can be exhaled during the first second of a forced exhalation. It is a reflection of the flow of air in the large airways of the lung, and is reduced in patients with COPD.
• Number Needed to Treat (NNT): The number of patients who need to be treated in order to achieve one additional favourable outcome.
• Relative Risk (RR): The ratio of the risk in the treated group to the risk in the control group.
• Relative Risk Reduction (RRR): The proportional reduction in the rates of bad outcomes between experimental and control participants in a trial.

### Resources

Using evidence to guide practice: what information is useful? Part of this reference explains the use of confidence intervals and illustrates them with some real examples.
RLO: Determining the clinical importance of trial results This RLO describes how to use ARR, RRR, NNT, NNH, and confidence intervals to interpret the results of clinical trials.
RLO: Numbers needed to treat (NNT) and numbers needed to harm (NNH) This RLO considers how to measure and interpret the magnitude of effect in clinical trial results using number needed to treat (NNT) and number needed to harm (NNH).
RLO: Positive and Negative Predictive Value of Diagnostic Tests Defines the term 'confidence intervals' and demonstrates how they can be used to determine the significance and range of possible sizes of a treatment effect.
RLO: Relative Risk Reduction (RRR) and Absolute Risk Reduction (ARR) This RLO considers how to measure and interpret the magnitude of effect in clinical trial results using relative risk reduction (RRR) and absolute risk reduction (ARR).
RLO: Sensitivity and Specificity This RLO explains how diagnostic test accuracy is described by the terms sensitivity and specificity. Sensitivity describes the accuracy of the test in detecting disease. Specificity describes the accuracy of the test in detecting health.
RLO: Surrogate Outcomes Considers the type of evidence which should be used when making decisions about patient care.

### Books and Journals

Straus E at al (2005) Evidence Based Medicine: How to practice and teach EBM. Elsevier Health (China).

### Confidence Intervals - Print summary

This RLO explains confidence intervals and demonstrates how they can be used to determine the significance of a treatment effect.

### Learning outcomes

By completing this resource, you should be able to describe how:

• confidence intervals can be used to assess the role of chance
• sample size affects the statistical significance of a trial.

By completing this resource, you will have learnt about confidence intervals. You should be able to describe how:

• confidence intervals can be used to assess the role of chance
• sample size affects the statistical significance of a trial.

### This resource was developed by:

Julia Lacey - content author

Neil Duffin, Liz Hilton - developers

The resource was originally funded by RLO-CETL.

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