A teacher thinks that whatever he says in class has no effect on his students. Just as he's about to quit his profession, a statistician enters the room and suggests that teacher design a study to test his assumption. The study will look at whether providing in-class feedback on homework assignments improves classroom performance.
The teacher desires to know whether providing feedback before or after returning assignments is most useful. He's also interested in the most effective means of presenting the feedback: verbal presentation, written handout, or a summary on overheads. Ultimately, he'd like to determine the best approach for increasing test scores of the students. There are 12 classes available in the school for the experiment.
Design an experiment that helps answer these questions. Be sure to identify the factors, the levels of the factors, the treatment groups, and the response variable. Comment on how the students will be assigned to the different treatment groups. Is it possible to use simple random assignment of all students? As much as possible, use diagrams instead of words to summarize your experimental design.