Workshop on Sample Size Planning for
Intensive Longitudinal Studies

Ginette Lafit, Jordan Revol, Mihai A. Constantin, & Eva Ceulemans

📝 Description

In recent years the popularity of procedures to collect intensive longitudinal data such as the Experience Sampling Method has increased immensely. The data collected using such designs allow researchers to study the dynamics of psychological processes, and how these dynamics differ across individuals. A fundamental question when designing a study is how to determine the sample size, which is closely related to the replicability and generalizability of empirical findings. Even though multiple statistical guidelines are available for sample size planning, it still remains a demanding enterprise in complex designs. The goal of this workshop is to address this crucial question by presenting methodological advances for sample size planning for intensive longitudinal designs. First, we provide an overview of methods for sample size planning with special emphasis on a priori power analysis. Second, we focus on how to conduct power analysis in the $N = 1$ case when the goal is to model within-person processes using $\text{VAR}(1)$ models. Subsequently, we consider the extension to multilevel data in which multiple individuals are measured over time. We introduce an approach for conducting power analysis for multilevel models that explicitly accounts for the temporal dependencies that characterize the data collected in IL studies. In addition, we showcase how to perform power analysis for these models using a user-friendly and open-source application. Finally, we consider an alternative criterion for conducting sample size planning that targets the predictive accuracy of a model for unseen data. Focusing on $\text{VAR}(1)$ models in an $N = 1$ context, we introduce a novel approach, called predictive accuracy analysis, to assess how many measurement occasions are required in order to optimize predictive accuracy.

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Check out the materials and more at
samplesize.help

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✍️ Citation

• Lafit, G., Revol, J., Constantin M. A., & Ceulemans, E. (2023). Workshop on Sample Size Planning for Intensive Longitudinal Studies. https://doi.org/10.5281/zenodo.8015940

⚖️ License

• The scripts, slides, and other materials by Ginette Lafit, Jordan Revol, Mihai A. Constantin, and Eva Ceulemans are licensed under CC BY 4.0 .