Do college professors who provide their students with assistance on homework help improve student grades? This was the research question of interest in the Journal of Accounting Education (Vol. 25, 2007). A sample of 175 accounting students took a pretest on a topic not covered in class, then each was given a homework problem to solve on the same topic. The students were assigned to one of three homework assistance groups. Some students received the completed solution, some were given check figures at various steps of the solution, and some received no help at all. After finishing the homework, the students were all given a posttest on the subject. The dependent variable of interest was the knowledge gain (or test score improvement). These data are saved in the ACCHW file.
a. Propose a model for the knowledge gain (y) as a function of the qualitative variable, homework assistance group.
b. In terms of the b's in the model, give an expression for the difference between the mean knowledge gains of students in the "completed solution" and "no help" groups.
c. Fit the model to the data and give the least squares prediction equation.
d. Conduct the global F-test for model utility using a = .05. Interpret the results practically.