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.
Walsh P, Rothenberg SJ.Walsh P, et al. Among authors: rothenberg sj.BMC Med Res Methodol. 2018 Nov 22;18(1):149. doi: 10.1186/s12874-018-0589-4.BMC Med Res Methodol. 2018.PMID: 30466396Free PMC article.