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Udogwu UN, Howe A, Frey K, Isaac M, Connelly D, Marinos D, Baker M, Castillo RC, Slobogean GP, O'Toole RV, O'Hara NN.Udogwu UN, et al.BMC Med Res Methodol. 2019 Dec 26;19(1):242. doi: 10.1186/s12874-019-0885-7.BMC Med Res Methodol. 2019.PMID: 31878874Free PMC article.