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 are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Wylie JL, Jolly AM.Wylie JL, et al.BMC Med Res Methodol. 2013 Jul 17;13:93. doi: 10.1186/1471-2288-13-93.BMC Med Res Methodol. 2013.PMID: 23865487Free PMC article.