15.5 An instructor at the University of Lige, Belgium, teaches a class of 28 students. At the...

15.5 An instructor at the University of Liège, Belgium, teaches a class of 28 students. At the beginning of the semester, each student is randomly assigned to one of four teaching assistants—Lucas, Emma, Arthur, or Sofia. The students are encouraged to meet with their assigned teaching assistant to discuss difficult course material. At the end of the semester, a common examination is administered. The scores obtained by students working with the teaching assistants are shown in the accompanying table.

Lucas Emma Arthur Sofia 29 53 23 37 42 40 34 38 33 39 24 50 22 32 43 48 46 49 30 41 24 36 27 35 55 45 31 38