title: Brackets (parentheses) in formulas.
authors.affiliation: Centre for Statistics in Medicine, University of Oxford, Oxford OX2 6UD. doug.altman@csm.ox.ac.uk
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Altman
authors.forename: J Martin
authors.initials: JM
authors.lastname: Bland
mesh_terms: D008433:Mathematics / Q000379:methods*; D012107:Research Design / Q000592:standards; D015983:Selection Bias