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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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Odds Ratio

Definition: The chance of an event occurring in one group compared to the chance of it occurring in another group. The odds ratio (OR) is a measure of effect size and is commonly used to compare results in clinical trials.

Example:

For example, a research study compared two groups of women who developed diabetes during their pregnancies. One group was treated with metformin, and the other group was treated with insulin. The researchers recorded how many of the mothers delivered their babies earlier than expected (less than 37 weeks after becoming pregnant). When they calculated the odds of an early delivery, the odds ratio (OR) for metformin was 1.06. This means that the women taking metformin had a small increase (1.06 times) in the odds of having an early delivery compared to the women taking insulin.

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