title: Efficient design and sample size calculation for trials with clustered data.
authors.affiliation: Maastricht University, the Netherlands gerard.vbreukelen@maastrichtuniversity.nl.
authors.forename: Gerard Jp
authors.initials: GJ
authors.lastname: van Breukelen
authors.affiliation: Maastricht University, the Netherlands.
authors.forename: Math Jjm
authors.initials: MJ
authors.lastname: Candel
mesh_terms: D016000:Cluster Analysis; D003627:Data Interpretation, Statistical; D006801:Humans; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012107:Research Design; D018401:Sample Size