To reduce or eliminate pseudoreplication, the coders also annotated the
effect size data using preestablished criteria to identify and report effect
sizes only from studies that represented independent courses and populations
reported. If the data reported were from iterations of the same
course at the same institution, we combined data recorded for more than one control and/or treatment group from the same experiment. We also
combined data from multiple outcomes from the same study (e.g., a series
of equivalent midterm examinations) (SI Materials and Methods). Coders
also extracted data on class size, course type, course level, and type of active
learning, when available.