Cook, Jonathan A.Julious, Steven A.Sones, WilliamHampson, Lisa V.Hewitt, CatherineBerlin, Jesse A.Ashby, DeborahEmsley, RichardFergusson, Dean A.Walters, Stephen J.Wilson, Edward C.F.MacLennan, GraemeStallard, NigelRothwell, Joanne C.Bland, MartinBrown, LouiseRamsay, Craig R.Cook, AndrewArmstrong, DavidAltman, DougVale, Luke D.2018-12-182018-12-182018-11-05Cook, J A, Julious, S A, Sones, W, Hampson, L V, Hewitt, C, Berlin, J A, Ashby, D, Emsley, R, Fergusson, D A, Walters, S J, Wilson, E C F, MacLennan, G, Stallard, N, Rothwell, J C, Bland, M, Brown, L, Ramsay, C R, Cook, A, Armstrong, D, Altman, D & Vale, L D 2018, 'DELTA 2 guidance on choosing the target difference and undertaking and reporting the sample size calculation for a randomised controlled trial', BMJ, vol. 363, k3750. https://doi.org/10.1136/bmj.k37500959-8146ORCID: /0000-0002-1039-5646/work/98038564http://hdl.handle.net/2164/11672Funding: Funding for this work was received from the MRC-NIHR UK Methodology Research Programme in response to an open commissioned call for an effect size methodology state-of-the-art workshop. The Health Services Research Unit, Institute of Applied Health Sciences (University of Aberdeen), is core funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. The funders had no involvement in study design, collection, analysis, and interpretation of data; reporting; or the decision to publish.285726engR MedicineGeneral MedicineMedical Research Council (MRC)National Institute for Health Research (NIHR)RJournal article10.1136/bmj.k3750http://www.scopus.com/inward/record.url?scp=85054779671&partnerID=8YFLogxK363