Version 1.1.0 Edited on December 16, 2022, to use the new as_draws_df() workflow. Purpose In the contemporary longitudinal data analysis literature, 2-timepoint data (a.k.a. pre/post data) get a bad wrap. Singer and Willett ( 2003, p. 10) described 2-timepoint data as only “marginally better” than cross-sectional data and Rogosa et al. ( 1982) give a technical overview on the limitations of 2-timepoint data. Limitations aside, sometimes two timepoints are all you have.
