Suppose that you have collected data throughout a semester from a large elementary school regarding the average number of days per week each math teacher spends in a collaborative teaching community. The average ranges from 0 to 7 days per week. You have also obtained the pre-test and post-test scores in math administered in those same classrooms in the beginning and end of the semester, and you have calculated a score that shows learning during the semester by subtracting the pre-test score from the post-test score for each student.
You are interested in examining any potential relationship between the average number of days of teacher collaborative activities and student learning (i.e., post-test minus pre-test). Is group comparison the best approach to analyze the available data? Why or why not?