An instructor has a class of 23 students. At the beginning of semester, each student is randomly allocated to one of the four teaching assistants- Sam, Denniel, Michael, and Robert. 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 score obtained by students working with these teaching assistants are shown in the accompanying table.

Sam Denniel Michael Robert 72.5 69.0 84.5 76.0 63.0

78.0 93.0 79.5 97.0 88.5 80.0

80.0 68.5 59.0 75.5 81.0 68.0

79.5 69.5 61.0 74.5 84.5 63.0

(a) Prepare the analysis of variance table for these data Test the null hypothesis that students working under different teaching assistants performed equally in the exam