The drivers' reaction time dataset used in these examples (evaluation_sleepstudy.csv) is from Belenky et al. (2003).
It can be retrieved from: https://benlambertdotcom.files.wordpress.com/2018/08/all_data.zip.
The PyMC3 code for the probabilistic homogenous, heterogenous, and hierarchical models mentioned in Chapters 1, 2, and 3 can be found in the driver_reaction_time.ipynb.