title: "Cross-sectional" stepped wedge designs always reduce the required sample size when there is no time effect.
authors.affiliation: Departments of Epidemiology and Biostatistics, Harvard T.H. Chan School of Public Health, 677 Hungtington Avenue, Boston, MA 02115, USA. Electronic address: stxzh@channing.harvard.edu.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: AbbVie Inc., Data and Statistical Sciences, 1 North Waukegan Road, North Chicago, IL 60064, USA.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Liao
authors.affiliation: Departments of Epidemiology and Biostatistics, Harvard T.H. Chan School of Public Health, 677 Hungtington Avenue, Boston, MA 02115, USA.
authors.forename: Donna
authors.initials: D
authors.lastname: Spiegelman
mesh_terms: D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D016032:Randomized Controlled Trials as Topic; D018401:Sample Size