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DianeKolb - 11 May 2009
Department of Biostatistics Seminar/Workshop Series
Sample Size Adjustments - It's About More Than A Formula
Rafe Donahue, PhD
Associate Director Statistics, BioMimetic Therapeutics, Inc. & Adjunct Faculty, Department of Biostatistics, Vanderbilt University School of Medicine
Wednesday, May 20, 1:30-2:30pm, MRBIII Conference Room 1220
Intended Audience: Persons interested in applied statistics, statistical theory, epidemiology, health services research, clinical trials methodology, statistical computing, statistical graphics, R users or potential users
Adjusting sample sizes based on interim analyses in on-going clinical trials is a hot topic in statistical literature. There are oodles of plans and schemes concerning how to update sample sizes in on-going clinical trials, complete with all the bells and whistles about maintaining Type I error rates. But these formula-based methods can be naive and short-sighted; as with almost everything in the real world, "it's more complicated than that."
I will recount a true story of sample-size updates in a real-life clinical trial and discuss how the straight-forward statistical approach was inadequate. I will present a methodology that allows one to do
unblinded early looks at the data and increase the sample size without suffering a Type I error penalty.
And, if time allows, I will present a demonstration of a Kelvin wheel-and-disk integrator (a mechanical analog computer that computes integrals) made entirely of Lego.