Living on campus. A February 2, 2008, article in the Columbus Dispatch reported a study on the distances students lived from campus and average GPA. Here is a summary of the results:

Residence Avg. GPA Residence hall 3.33 Walking distance 3.16 Near campus, long walk or short drive 3.12 Within the county, not near campus 2.97 Outside the county 2.94 Based on these data, the association between the distance a student lives from campus and GPA is negative. Many universities require freshmen to live on campus, but these data have prompted some to suggest that sophomores should also be required to live on campus in order to improve grades. Do these data imply that living closer to campus improves grades? Why?