Research Associate, The Methodology Center
The Methodology Center
The Pennsylvania State University
400 Calder Square II
State College, PA 16801
814-863-9806
Education
Ph.D., The Pennsylvania State University, 2006 (Statistics)
M.S., The Pennsylvania State University, 2004 (Statistics)
M.A., The Catholic University of America, 2001 (Psychology)
B.S., The University of Scranton, 1999 (Psychology)
Current Projects and Collaborators
One of my main roles here at the Center is working on software development, in particular for our SAS procedures. I helped expand the functionality of our latent class analysis procedure PROC LCA, to allow for standard error estimation and for pseudolikelihood estimation with sampling weights. I am very interested in the analysis of longitudinal data and am working with Runze Li, Xianming Tan, and Mariya Shiyko on some research related to a variation of the Time-Varying Effect Model.
I’ve also been working with Linda Collins and Inbal Nahum-Shani on studying analysis models and statistical power for experimental designs to study multiple-factor interventions. We are interested in the special challenges that arise in common situations in which study participants must be treated in clusters such as teams, schools or hospitals rather than being treated as individuals. This nested structure changes the way the study must be planned, performed, and analyzed.
Last, I’ve been working on a project with Stephanie Lanza and Xianming Tan on a study in which we used PROC LCA in an extensive series of Monte Carlo simulation experiments to try to find a way to predict the statistical power of the bootstrap test forcomparing LCA models with different numbers of latent classes.
Research Interests
Currently most of my work is with simulations, especially for studying statistical power, and particularly in challenging situations such as factor-screening experiments and/or clustered datasets. I am also interested in model selection, latent class and variable models, and the modeling of longitudinal data. My thesis had to do with on the application of the smoothly clipped absolute deviation variable selection complexity penalty to objective functions other than likelihoods, such as generalized least squares and quadratic inference functions.
Methodology Center Research Areas:
Publications
Peer-Reviewed Articles
Dziak, J. J., Lanza, S. T., & Tan, X. (in press). Effect size, statistical power and sample size requirements for the bootstrap likelihood ratio test in latent class analysis. Structural Equation Modeling.
Dziak, J., Nahum-Shani, I. R., & Collins, L. M. (2012). Multilevel factorial experiments for developing behavioral interventions: Power, sample size, and resource considerations. Psychological Methods. Advance online publication. doi: 10.1037/a0026972 PMCID: PMC3351535
Collins, L. M., Dziak, J. J., & Li, R. (2009). Design of experiments with multiple independent variables: A resource management perspective on complete and reduced factorial designs. Psychological Methods, 14(3), 202-224. PMCID: PMC2796056
Book Chapters
Dziak, J. J., Li, R., & Qu, A. (2009). An overview on quadratic inference function approaches for longitudinal data. In J. Fan, X. Lin & J. S. Liu (Eds.), New developments in biostatistics and bioinformatics. Singapore: World Scientific.
Dziak, J. J., & Li, R. (2007). An overview on variable selection for longitudinal data. In D. Hong (Ed.), Quantitative medical data analysis (pp. 5-24). Singapore: World Sciences Publishers.
Presentations
Collins, L. M., Dziak, J. J., & Nahum-Shani, I. (2012, July). Fractional factorial experiments and cluster randomization: An integration of engineering research methods and educational research methods. Presented at the Institute of Mathematical Statistics Asia-Pacific Rim Meeting, Tskuba, Japan.
Dziak, J. J., Nahum-Shani, I., & Collins, L. M. (2012, June). Multilevel factorial experiments for developing behavioral interventions. In Alcohol and drug prevention for student-athletes: An application of the multiphase optimization strategy (MOST) in a multilevel setting. Presented at the 20th Annual Meeting of the Society for Prevention Research, Washington, DC.
Dziak, J. J., Li, R., Tan, X., Lanza, S. T., & Shiffman, S. (2012, March). Nonlinear latent class growth modeling of affect during smoking cessation. Poster presented at The Annual Meeting of the Society for Research on Nicotine and Tobacco, Houston, TX.
Dziak, J. J., Huang, L., Lanza, S. T., Li, R., Collins, L. M., & Xu, S. (2011, June). Software advances from the Methodology Center at Penn State. Technology demonstration presented at the Society for Prevention Research Annual Meetings, Washington, DC.
Dziak, J. J., Coffman, D. L., Lanza, S. T., & Li, R. (2011, June). Sensitivity and specificity of information criteria for model selection in prevention and psychology datasets. Poster prsented at the Society for Prevention Research Annual Meetings, Washington, DC.
Collins, L. M., Dziak, J. J., Huang, L., Lanza, S. T., Li, R., & Tan, X. (2010, June). New development of statistical software for prevention research in the Methodology Center. Technology demonstration presented at the annual meeting of the Society for Prevention Research, Denver, CO.
Software and Documentation
Lanza, S. T., Dziak, J. J., Huang, L., Wagner, A. T. , & Collins, L. M. (2013). LCA Stata Plugin users' guide (Version 1.0). University Park: The Methodology Center, Penn State. Available from methodology.psu.edu.
LCA Stata Plugin (Version 1.0) [Software]. (2013). University Park: The Methodology Center, Penn State. Retrieved from methodology.psu.edu
PROC QLEARN (Version 1.0) [Software] (2012). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Ertefaie, A., Almirall, D. A., Huang L., Dziak, J. J., Wagner, A. T., & Murphy, S. A. (2012). SAS PROC QLEARN users’ guide (Version 1.0). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Lca Distal SAS Macro (Version 1.1.0) [Software]. (2011). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Dziak, J. J., Lanza, S. T., & Xu, S. (2011). LcaBootstrap SAS macro users' guide (Version 1.1.0). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Dziak, J. J., Lanza, S. T., & Xu, S. (2011). SimulateLcaDataset SAS macro users' guide (Version 1.1.0). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Lanza, S. T., Dziak, J. J., Huang, L., Xu, S., & Collins, L. M. (2011). PROC LCA & PROC LTA users' guide (Version 1.2.6). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Lanza, S. T., Dziak, J. J., Huang, L., Xu, S., & Collins, L. M. (2011). PROC LCA & PROC LTA users' guide (Version 1.2.7). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Latent class analysis with a binary distal outcome [Software]. (2011). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
LcaBootstrap SAS macro (Version 1.1.0) [Software]. (2011). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
PROC LCA & PROC LTA (Version 1.2.6) [Software]. (2011). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
PROC LCA & PROC LTA (Version 1.2.7) [Software]. (2011). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
SimulateLcaDataset SAS macro (Version 1.1.0) [Software]. (2011). University Park: The Methodology Center, Penn State. Retrieved from http://methodology.psu.edu
Dziak, J. J., & Lanza, S. T. (2010, May). SAS graphics macros for latent class analysis (Version 1.0). [Software]. University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
Dziak, J. J., & Lanza, S. T. (2010, May). SAS graphics macros for latent class analysis users' guide (Version 1.0). University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
The Methodology Center. (2010, May). PROC SCADGLIM (Version 1.1 alpha). [Software]. University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
Dziak, J. J., Lemmon, D. R., Li, R., & Huang, L. (2010, May). PROC SCADGLIM users' guide (Version 1.1 alpha). University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
The Methodology Center. (2010, May). PROC SCADLS (Version 1.1 beta). [Software]. University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
Dziak, J. J., Lemmon, D. R., Li, R., & Huang, L. (2010, May). PROC SCADLS users' guide (Version 1.1. beta). University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
The Methodology Center. (2010, May). PROC LCA & PROC LTA Version 1.2.5 beta. [Software]. University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
Lanza, S. T., Lemmon, D. R., Dziak, J. J., Huang, L., Schafer, J. L., & Collins, L. M. (2010, May). PROC LCA & PROC LTA users' guide (Version 1.2.5 beta). University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
The Methodology Center. (2010, February). PROC LCA & PROC LTA (Version 1.2.4 beta). [Software]. Written in Fortran and SAS Toolkit. University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu
Lanza, S. T., Lemmon, D. R., Dziak, J. J., Huang, L., Schafer, J. L., & Collins, L. M. (2010, February). PROC LCA & PROC LTA users' guide (Version 1.2.4 beta). University Park: The Methodology Center, Penn State. Available at http://methodology.psu.edu