4. Do university professors who provide their students with assistance on homework. help improve student grades? A sample of ITS aecotmting 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 gures at various steps of the solution, and some received no help at all. After finishing the homework. the students were all given a post test on the subject. The dependent variable of interest was the knowledge gain [or test score improvement}. The data are saved in the ACCHWJXT le. a. Propose a model for the knowledge gain [3?] as a function of the qualitative variableI homework assistance group. [2] b. In terms of the [1's in the model, given an expansion for the difference between the mean knowledge gains of students in the \"completed solution\" and \"no help\" groups. {2} c. Fit the model to the data and give the least squares prediction equation. (4} d. lConduct the global Ftest for model utilityr using u=l}.l}5. hrterpret the results practically. [4)