title: Estimating sample size for continuous outcomes, comparing more than two parallel groups with unequal sizes.
abstract: This paper contains a short generalization of a known method for sample size determination in the case of more than two parallel groups. The term 'set of allocation ratios' corresponding to the allocation ratio from the two-group design is defined. A formula using these ratios to determine the non-centrality parameter of the F distribution is deduced. It is shown that in case of more than two groups, equal group numbers does not constitute an optimal design. Two worked examples are presented.
authors.affiliation: Chinoin Pharmaceutical and Chemical Works Ltd., Clinical Research Unit, Budapest, Hungary.
authors.forename: J
authors.initials: J
authors.lastname: Singer
mesh_terms: D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology; D006801:Humans; D012107:Research Design; D018401:Sample Size