An advertising company is interested in determining if there is a difference in the mean salesthatwillbegeneratedforasoftdrinkcompanybasedonwhichshelfthesoftdrinksarelocated.There are four possible shelf levels. The ad company wants to control for store size. Thefollowingdatareflectthe salesforone weekateachcombinationofshelflevelandstoresize.

Level 1 Level 2 Level 3 Level 4 Small Store 300 200 500 200 Medium Store 400 180 600 200 Large Store 600 300 900 400