Research design
In the recitation / tutorial experiment, only one hour of instruction per week was modified.
Ten different faculty taught the classes — only one of them the researcher.
Two instructors taught twice— once with recitations and once with tutorials. In both cases the tutorial result was substantially better than the recitation result. (Dh > 0.15)
* E. F. Redish, J. M. Saul, and R. N. Steinberg, Am. J. Phys. 65, 45-54 (1997)