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Glossary of Terms

We know that many of the concepts used on this site can be difficult to understand. For that reason, we have provided you with a glossary to help you make sense of the terms used in Comparative Effectiveness Research. Every word that is defined in this glossary should appear highlighted throughout the Web site. When you come upon a highlighted term and would like to read the full definition, you can either click on the word to visit the glossary or roll your mouse over the word for a pop-up definition.

 

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Relative Risk

Definition: A comparison of the risk of a particular event for different groups of people. Relative risk (RR) is usually used to estimate exposure to something that could affect health. In a clinical research study, the experimental group is exposed to a particular drug or treatment. The control group is not. The number of events in each group is compared to determine relative risk.

Example:

For example, researchers analyzed information from a group of different studies that looked at the number of people who had stomach bleeding when taking the drug ibuprofen. They found that people who took ibuprofen were 2½ times more likely to have stomach bleeding than those who did not take ibuprofen. The relative risk of having stomach bleeding while taking ibuprofen was 2.5 (RR 2.5) in these studies.

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