DEPARTMENT OF STATISTICS
Joint UConn - UMass Statistics Colloquium
The Department of Statistics Cordially Invites You
To a Colloquium
John Staudenmayer, Assoc. Professor
Department of Mathematics and Statistics
University of Massachusetts, Amherst
Methods to Assess an Exercise Intervention Trial based on Three-Level Functional Data
Abstract
Motivated by data recording the effects of an exercise intervention on subjects' physical activity over time, we develop a model to assess the effects of a treatment when the data are functional with three levels and possibly incomplete data. We develop a three-level model with week, day, and week x day interaction mean structure effects, all stratified by treatment, and subject random effects including a general subject effect and nested effects for weeks, days, and week-by-day interactions. The mean and random structures are specified as smooth curves measured at various time-points. The association structure of the three-level data is induced through the random curves, which are summarized using a few important principal components. We use penalized splines to model the mean curves and the principal component curves, and cast the proposed model into a mixed effects model framework for model fitting, prediction and inference. We develop an algorithm to fit the model iteratively with the ECME version of the EM algorithm and eigenvalue decompositions. Selection of the number of principal components and handling incomplete data issues are incorporated into the algorithm. The performance of the Wald-type hypothesis test is also discussed. The method is applied to the physical activity data and evaluated empirically by a simulation study.
This is joint work with Haocheng Li, Houssein Assaad, Jianhua Huang, and Raymond Carroll from the Department of Statistics, Texas A&M University and Sarah Kozey-Keadle from the Nutritional Epidemiology Branch, National Cancer Institute.
DATE: Wednesday, April 9, 2014
TIME: 4:00 p.m.
PLACE: Philip E. Austin Building (AUST) Room 105
Coffee will be served at 3:30 p.m. (AUST 326)
For more information, contact: Tracy Burke at tracy.burke@uconn.edu