title: Practical usage of O'Brien's OLS and GLS statistics in clinical trials.
abstract: Multivariate techniques of O'Brien's OLS and GLS statistics are discussed in the context of their application in clinical trials. We introduce the concept of an operational effect size and illustrate its use to evaluate power. An extension describing how to handle covariates and missing data is developed in the context of Mixed models. This extension allowing adjustment for covariates is easily programmed in any statistical package including SAS. Monte Carlo simulation is used for a number of different sample sizes to compare the actual size and power of the tests based on O'Brien's OLS and GLS statistics.
authors: GlaxoSmithKline, Greenford, UK.
authors: Nigel S
authors: NS
authors: Dallow
authors: Sergei L
authors: SL
authors: Leonov
authors: James H
authors: JH
authors: Roger
mesh_terms: D015415:Biomarkers / Q000032:analysis; D002986:Clinical Trials as Topic / Q000706:statistics & numerical data*; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D006801:Humans; D015233:Models, Statistical; D009010:Monte Carlo Method; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism; D015203:Reproducibility of Results; D012107:Research Design; D012984:Software; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers