Join us for the third CCASA 2011-2012 luncheon!
We are pleased to announce that our speaker will be Dulal K. Bhaumik PhD, Professor of Biostatistics,
Psychiatry and Bioengineering at the University of Illinois at Chicago.
Professor Bhaumik will be speaking on Sample Size Determination
for Three-level Longitudinal Models with Differential Attrition.
Abstract: We consider the problem of sample size determination for
three-level mixed-effects linear regression models for the analysis of
clustered longitudinal data. Three-level designs are used in many areas,
but in particular, multicenter randomized longitudinal clinical trials
in medical or health-related research. In this case, level 1 represents
measurement occasion, level 2 represents subject, and level 3 represents
center. The model we consider involves random effects of the time
trends at both the subject level and the center level. In the most
common case, we have two random effects (constant and a single trend),
at both subject and center levels. The approach presented here is
general with respect to sampling proportions, number of groups, and
attrition rates over time.
In addition, we also develop a cost model, as an aid in selecting the
most parsimonious of several possible competing models (i.e., different
combinations of centers, subjects within centers, and measurement
occasions). We derive sample size requirements (i.e., power
characteristics) for a test of treatment-by-time interaction(s) for
designs based on either subject-level or cluster-level randomization.
The general methodology is illustrated using two characteristic examples.
Click the the link below to register for the luncheon!