Clinical Research Glossary

hazard ratio hazard ratio


A measure of risk that compares two treatments in the same study.

Example of hazard ratio in a sentence

Studies with more than one group use hazard ratios to compare whether one group has more adverse events than the other.

More Info

The hazard ratio is the relative risk of an event happening in one group compared to another.

For example, in a drug study, the group getting the study treatment may have headaches two times more than the control population. The hazard ratio would be 2, meaning that the study treatment group has twice the chance of getting headaches compared to the comparison group.

Other info to think about when joining a study

You might see the word “hazard ratio” in research reports and articles that describe the results of research studies. This is a technical math term and will not usually be used in materials designed especially for patients and participants.

If you see this word in a study document for a study you are considering, enrolled in, or completed, you can ask the researcher or study team any questions you might have.

An icon consisting of a circle with a calculator, graph paper with a bar chart and a bell curve drawn on, and a pencil. This icon represents all the math terms in this glossary.
This graphic represents math and statistics terms in this glossary.

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