title: The importance of potential studies that have not existed and registration of observational data sets.
authors.affiliation: Stanford Prevention Research Center, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA. jioannid@stanford.edu
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
mesh_terms: D016022:Case-Control Studies; D002986:Clinical Trials as Topic; D015331:Cohort Studies; D003625:Data Collection / Q000379:methods; D005544:Forecasting; D006801:Humans; D019370:Observation; D017594:Publication Bias; D012042:Registries / Q000706:statistics & numerical data*; D012107:Research Design