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.
Jabre JF, Bland JDP.Jabre JF, et al.BMC Med Res Methodol. 2021 Feb 22;21(1):40. doi: 10.1186/s12874-021-01222-z.BMC Med Res Methodol. 2021.PMID: 33618666Free PMC article.