Mastering Econometrics (Marginal Revolution University)

If you only add one course after the principles, make it this one. Joshua Angrist, who shared the 2021 economics Nobel for work on cause and effect, teaches the five methods economists use to tell whether a policy did anything: random assignment, regression, instrumental variables, regression discontinuity and difference-in-differences. The lessons on selection bias and ceteris paribus reasoning are the most useful defense there is against a report claiming a program worked because its participants did better. The course runs to about twenty lessons with quizzes, and after it you will read the methods paragraph of a study before the conclusion.