Wednesday, August 12th, 2009 exceeded my expectations in so many ways. I was really touched by having so many people in attendance for my dissertation defense. Friends and professors from math & stat, biology, and other departments, collaborators from the medical campus and from consulting outside the university, and my mom and brother. About 25-30 in all.
Dissertation defense for Erik Barry Erhardt, PhD candidate in Statistics
Wednesday, August 12th at 10am in Humanities 428
University of New Mexico
The Wishart distribution and especially the inverse-Wishart distribution are the source of some confusion because they occasionally appear with alternative parameterizations. Also, the Wishart distribution can be used to model a covariance matrix or a precision matrix (the inverse of a covariance matrix) in different situations, and the inverse-Wishart the same, but the other way round. It’s already becoming complicated. Hal Stern, coauthor of Bayesian Data Analysis (BDA), helped to clarify many issues for me in an email conversation. In this post I hope to clarify the differences in Wishart parameterizations of BDA, the wikipedia pages, and the WinBUGS and OpenBUGS softwares, and show an example in OpenBUGS where the inverse parameterization has to be specified relative to the distribution’s definition for the correct posterior to result.
Seymour Grufferman, Frederick Ruymann, Simona Ognjanovic, Erik B. Erhardt, and Harold M. Maurer.
Prenatal X-ray Exposure and Rhabdomyosarcoma in Children: A Report from the Children’s Oncology Group. Cancer Epidemiology Biomarkers & Prevention. April 2009, 18(4), OF1–6. [pdf]
On Jan 20th, 2009, I joined the Medical Image Analysis Laboratory (MIALab) as a research assistant (RA) at the MIND institute at UNM. This position will transition to a 2-3 year postdoc upon the completion of my PhD this May.
Christopher P. Bickford, Nate G. Mcdowell, Erik Barry Erhardt, Heath H. Powers, David T. Hanson. (2009)
“High frequency field measurements of diurnal carbon isotope discrimination and internal conductance in a semi-arid species, Juniperus monosperma“.
Plant, Cell & Environment, online
Volume 32, Issue 7, pages 796–810, July 2009.