The Authors
Brady West is a senior statistician and statistical software consultant at the Center for
Statistical Consultation and Research (CSCAR) at the University of Michigan–Ann Arbor.
He received a B.S. in statistics (2001) and an M.A. in applied statistics (2002) from the
University of Michigan–Ann Arbor. Mr. West has developed short courses on statistical
analysis using SPSS, R, and Stata, and regularly consults on the use of procedures in SAS,
SPSS, R, Stata, and HLM
for the analysis of longitudinal and clustered data.
Kathy Welch is a senior statistician and statistical software consultant at the Center for
Statistical Consultation and Research (CSCAR) at the University of Michigan–Ann Arbor.
She received a B.A. in sociology (1969), an M.P.H. in epidemiology and health education
(1975), and an M.S. in biostatistics (1984) from the University of Michigan (UM). She
regularly consults on the use of SAS, SPSS, Stata, and HLM for analysis of clustered and
longitudinal data, teaches a course on statistical software packages in the University of
Michigan Department of Biostatistics, and teaches short courses on SAS software. She has
also co-developed and co-taught short courses on the analysis of linear mixed models and
generalized linear models using SAS.
Andrzej Gałecki is a research associate professor in the Division of Geriatric Medicine,
Department of Internal Medicine, and Institute of Gerontology at the University of Mich-
igan Medical School, and has a joint appointment in the Department of Biostatistics at the
University of Michigan School of Public Health. He received a M.Sc. in applied mathe-
matics (1977) from the Technical University of Warsaw, Poland, and an M.D. (1981) from
the Medical Academy of Warsaw. In 1985 he earned a Ph.D. in epidemiology from the
Institute of Mother and Child Care in Warsaw (Poland). Since 1990, Dr. Gałecki has
collaborated with researchers in gerontology and geriatrics. His research interests lie in
the development and application of statistical methods for analyzing correlated and over-
dispersed data. He developed the SAS macro NLMEM for nonlinear mixed-effects models,
specified as a solution of ordinary differential equations. In a 1994 paper, he proposed a
general class of covariance structures for two or more within-subject factors. Examples of
these structures have been implemented in SAS Proc Mixed.
Brenda Gillespie is the associate director of the Center for Statistical Consultation and
Research (CSCAR) at the University of Michigan in Ann Arbor. She received an A.B. in
mathematics (1972) from Earlham College in Richmond, Indiana, an M.S. in statistics (1975)
from The Ohio State University, and earned a Ph.D. in statistics (1989) from Temple
University in Philadelphia, Pennsylvania. Dr. Gillespie has collaborated extensively with
researchers in health-related fields, and has worked with mixed models as the primary
statistician on the Collaborative Initial Glaucoma Treatment Study (CIGTS), the Dialysis
Outcomes Practice Pattern Study (DOPPS), the Scientific Registry of Transplant Recipients
(SRTR), the University of Michigan Dioxin Study, and at the Complementary and Alter-
native Medicine Research Center at the University of Michigan.
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