title: Why analysis of variance is inappropriate for multiclinic trials.
abstract: Violations of the assumptions behind analysis of variance (ANOVA) models do not tend to affect the alpha-level but can greatly decrease the power of a clinical trial to detect treatment effects. The very nature of multiclinic studies guarantees the violation of some of these assumptions. In this article, I explore the reduction in power that results from two of these violations--heterogeneity of variance across sites and the existence of "floor" and "ceiling" effects. I propose other methods of statistical analysis that avoid this loss of power.
authors.forename: D
authors.initials: D
authors.lastname: Salsburg
mesh_terms: D000704:Analysis of Variance; D006801:Humans; D015337:Multicenter Studies as Topic / Q000379:methods*; D018579:Patient Selection; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D018401:Sample Size; D018709:Statistics, Nonparametric