An official website of the United States government
Here’s how you know
The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.
The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.
A type of clinical trial that includes a control arm. Outcomes in the control arm are compared with those in the experimental arm to determine any differences, for example, in safety and effectiveness.