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.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Randomization

A method of assigning participants in clinical trials into two or more groups randomly (by chance). One group receives the treatment or drug being researched, and one group receives either no treatment, a placebo (inactive substance), or another drug. Participants are assigned to a group by various methods. detail

Randomized Controlled Trial

A controlled clinical trial that randomly (by chance) assigns participants to two or more groups. There are various methods to randomize study participants to their groups. detail

Relative Risk

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. detail

Risk

A way of expressing the chance that something will happen. It is a measure of the association between exposure to something and what happens (the outcome). Risk is the same as probability, but it usually is used to describe the probability of an adverse event. It is the rate of events (such as breast cancer) in the total population of people who could have the event (such as women of a certain age). detail

Risk Factor

A characteristic of a person that affects that person's chance of having a disease. A risk factor may be an inherent trait, such as gender or genetic make-up, or a factor under the person's control, such as using tobacco. A risk factor does not usually cause the disease. It changes a person's chance (or risk) of getting the disease. detail

Risk/Benefit Ratio

A method for comparing a treatment's benefits and risks, such as curing a disease (benefit) versus having a serious side effect from the treatment (risk). The risk/benefit ratio of a treatment is different depending on the disease or condition being treated. detail