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Ensor J, Burke DL, Snell KIE, Hemming K, Riley RD.Ensor J, et al.BMC Med Res Methodol. 2018 May 18;18(1):41. doi: 10.1186/s12874-018-0492-z.BMC Med Res Methodol. 2018.PMID: 29776399Free PMC article.