College of Education and Human Development

Department of Educational Psychology

Longitudinal Methods Development (LMD) Lab

LMD lab members

Members of the LMD lab pose with pillows printed with their first authored papers.

LMD lab members


  • Development and extension of statistical methodologies that effectively describe different underlying intrinsically nonlinear patterns of change
  • Evaluation of the robustness (including accuracy and precision) of the methods developed or extended via Monte Carlo Simulation techniques
  • Provide researchers and practitioners with the theoretical underpinnings and empirical guidance on how to effectively utilize these techniques to address important substantive questions in education and psychology.

Current projects

  • Development of Bayesian Piecewise Crossed Random Effects Model
  • Evaluation of Model Identification Issues for Crossed Random Effects Model
  • Incorporating Covariates in Bayesian Piecewise Growth Mixture Models
  • Global Model Fit Indices for Random Effects Models

Research group

Nidhi Kohli headshot

Nidhi Kohli

Lab director

Royal and Virginia Anderson Professor of Quantitative Methods in Education, Department of Educational Psychology

Corissa Rohloff

Curriculum Vitae (PDF)

Corissa's research includes model development, estimation, and selection for intrinsically nonlinear (crossed) random effects models from both Maximum Likelihood and Bayesian inference perspectives. Her main focus is on the analysis of repeated measures data using complex functional forms. More specifically, Corissa has explored how functional form impacts model selection and whether functional form complexity should be taken into consideration when researchers evaluate the appropriateness of their models. She has also extended the piecewise random effects model with unknown knots to incorporate crossed random effects (e.g., student and teacher random effects on growth) using Bayesian inference. Currently, Corissa is working to disseminate an R package to allow researchers to estimate various nonlinear longitudinal models (e.g., mixture, crossed random effects, bivariate).

In 2022, she received the American Educational Research Association (AERA) Educational Statistics Special Interest Group (SIG) Best Graduate Student Paper Award for her paper, “The Impact of Functional Form Complexity on Model Overfitting for Nonlinear Mixed-Effects Models.” In 2023, Corissa was a recipient of the Russell W. Burris Memorial Fellowship in Educational Psychology. This fellowship was established in memory of Russell Burris, professor emeritus of educational psychology. Dr. Burris studied what and how we learn, in particular “expertness,” focusing on areas that included trial advocacy, clinical medicine, and art history.

Ziwei Zhang headshot

Ziwei Zhang

Curriculum Vitae (PDF)

Ziwei is interested in topics related to model development, estimation, and evaluation of intrinsically linear and nonlinear models for longitudinal data, specifically in the random effects modeling (REM) framework. In her first methodological project, she translated global model fit indices from the latent growth curve modeling framework to REM for intrinsically linear and nonlinear models. This helps researchers to evaluate the overall fit of a random effects model to data without employing model comparison approach. In her current project, she has developed a Bayesian random effects mediation model to examine mediation effects on longitudinal outcomes with intrinsically linear or nonlinear functions. Additionally, she has explored the impact of omitting confounders on the overall model performance of longitudinal mediation models. Ziwei is motivated to continue to provide flexible statistical modeling options, including model fit indices, within REM to a wider audience of methodologists and applied researchers.

Yue Zhao headshot

Yue Zhao

Yue is a first-year PhD student in the QME program. She is interested in developing and applying longitudinal statistical models for educational and psychological data. She believes that each data set has its unique features, therefore her focus is developing and/or extending statistical models to address the uniqueness of each data set.

Past PhD students

Yadira Peralta headshot

Yadira Peralta-Torres

Current position: Assistant professor in the Department of Economics at the Center for Research and Teaching in Economics (CIDE), Mexico

Rik Lamm headshot

Rik Lamm

Current position: Research, Evaluation, and Assessment Scientist in the Department of Research, Evaluation, and Assessment at the Bloomington Public Schools, MN

Recent publications

*Rohloff, C. T., Kohli, N., & Lock, E. F. (in press, 2024). Identifiability and estimability of Bayesian linear and nonlinear crossed random effects models. British Journal of Mathematical & Statistical Psychology. DOI:

*Peralta, Y., Kohli, N., Kendeou, P., Davison, M. L., & Lock, E. F. (in press, 2023). Modeling the interrelation of reading and mathematics achievement trajectories: Is their development intertwined? Reading and Writing.

*Zhang, Z., *Rohloff, C. T., & Kohli, N. (2023). Model fit indices for random effects models: Translating model fit ideas from latent growth curve models. Structural Equation Modeling: A Multidisciplinary Journal, 30(5), 822–830.

*Rohloff, C. T., Kohli, N., & Chung, S. (2023). The impact of functional form complexity on model overfitting for nonlinear mixed-effects models. Multivariate Behavioral Research, 58(4), 723–742.

*Zhang, Z., *Rohloff, C. T., & Kohli, N. (2023). Commentary on “Obtaining interpretable parameters from reparameterized longitudinal models: Transformation matrices between growth factors in two parameter-spaces”. Journal of Educational and Behavioral Statistics, 48(2), 262–268.

*Peralta, Y., Kohli, N., Lock, E. F., and Davison, M. L. (2022). Bayesian modeling of associations in bivariate piecewise linear mixed-effects models. Psychological Methods,27(1), 44–64.

Kohli, N., & Sullivan, A. L. (2019). Linear-Linear piecewise growth mixture models with unknown random knots: A primer for School Psychology. Journal of School Psychology, 73, 89–100.

Kohli, N., *Peralta, Y., & *Bose, M. (2019). Piecewise random-effects modeling software programs. Structural Equation Modeling: A Multidisciplinary Journal, 26(1), 156–164.

*Peralta, Y., Kohli, N., & Wang, C. (2018). A primer on distributional assumptions and model linearity in repeated measures data analysis. Quantitative Methods for Psychology, 14(3), 199–217, DOI: doi:10.20982/tqmp.14.3.p199.

Lock, E. F., Kohli, N., & *Bose, M. (2018). Detecting multiple random changepoints in Bayesian piecewise growth mixture models. Psychometrika, 83(3), 733–750.

Kohli, N., *Peralta, Y., *Zopluoglu, C., & Davison, M. L. (2018). A note on estimating single-class piecewise mixed effect models with unknown change points. International Journal of Behavioral Development—Method & Measures Section, 42(5), 518–524.

Harwell, M. R., Kohli, N., & *Peralta, Y. (2018). A survey of reporting practices of computer simulation studies in statistical research. American Statistician, 72(4), 321–327.

Harwell, M. R., Kohli, N., & *Peralta, Y. (2017). Experimental design and data analysis in computer simulation studies in the behavioral sciences. Journal of Modern Applied Statistical Methods, 16(2), 3–28.

Sullivan, A. L., Kohli, N., Farnsworth, E. M., Jones, L., & Sadeh, S. (2017). Longitudinal models of reading achievement of students with and without learning disabilities. School Psychology Quarterly, 32(3), 336–349.

Kohli, N., Harring, J. R., & *Zopluoglu, C. (2016). A finite mixture of nonlinear random coefficient models for continuous repeated measures data. Psychometrika, 81(3), 851–880.

Wang, C., Kohli, N., & *Henn, L. (2016). A second-order longitudinal model for binary outcomes: Item response theory versus factor analytic framework. Structural Equation Modeling: A Multidisciplinary Journal, 23(3), 455–465.

Kohli, N., Hughes, J., Wang, C., *Zopluoglu, C., & Davison, M. L. (2015). Fitting a linear–linear piecewise growth mixture model with unknown knots: A comparison of two common approaches to inference. Psychological Methods, 20(2), 259–275.

Kohli, N., Koran, J., & *Henn, L. (2015). Relationships among classical test theory and item response theory frameworks via factor analytic models. Educational and Psychological Measurement, 75(3), 389–405.

Kohli, N., Sullivan, A. L., Sadeh, S. S., & *Zopluoglu, C. (2015). Longitudinal mathematics development of students with learning disabilities and students without disabilities: A comparison of linear, quadratic, and piecewise mixed effects models. Journal of School Psychology, 53(2), 105–120. [The first author received the following financial support for the research, authorship, and publication of this article: U of M Grant-in-Aid of Research, Artistry & Scholarship Program]

*Zopluoglu, C., Harring, J. R., & Kohli, N. (2014). FitPMM: An R routine to fit finite mixture of piecewise mixed–effect models with unknown random knots. Applied Psychological Measurement, 38(7), 583–584.

Kohli, N., Harring, J. R., & Hancock, G. R. (2013). Piecewise linear–linear latent growth mixture models with unknown knots. Educational and Psychological Measurement, 73(6), 935–955.

Kohli, N., & Harring, J. R. (2013). Modeling growth in latent variables using a piecewise function. Multivariate Behavioral Research, 48(3), 370–397.

*Indicates co-author was an UMN student during part or all of the work