An official website of the United States government
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're connecting to the official website and that any information you provide is encrypted and sent securely.
If you are a Veteran in crisis or concerned about one, connect with our caring, qualified responders for confidential help. Many of them are Veterans themselves.
Nelson DB. Propensity Scores and Related Summaries. Paper presented at: Task Force on Design and Analysis in Oral Health Research Scientific Session; 2009 Nov 10; Newark, NJ.