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.2018-11-262018-11-262018-11-05Cook, 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', Trials, vol. 19, 606. https://doi.org/10.1186/s13063-018-2884-01745-6215ORCID: /0000-0003-4043-7349/work/84131314ORCID: /0000-0002-1039-5646/work/98038507http://hdl.handle.net/2164/11519Funding Funding for this work was received from the MRC/NIHR MRP 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.1205125engR MedicineMedicine (miscellaneous)Pharmacology (medical)RJournal article10.1186/s13063-018-2884-0http://www.scopus.com/inward/record.url?scp=85056093774&partnerID=8YFLogxK19