title: Assembling comparison groups to assess the effects of health care.
authors.affiliation: UK Cochrane Centre, NHS Research & Development Programme, Oxford, England.
authors.forename: I
authors.initials: I
authors.lastname: Chalmers
mesh_terms: D018849:Controlled Clinical Trials as Topic / Q000379:methods*; D004992:Ethics, Medical; D006801:Humans; D019300:Medical Errors; D015201:Meta-Analysis as Topic; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D015983:Selection Bias