Professor Stone complains that students’ teacher ratings depend on the grade students receive. In other words, according to Professor Stone, a teacher who gives good grades gets good ratings, and a teacher who gives bad grades gets bad ratings. To test this claim, the Student Assembly took a random sample of 300 teacher ratings on which the students’ grades for the course also were indicated. The results are given in the following table. Test the hypothesis that teacher ratings and student grades are independent at the 0.01 level of signifi­cance.

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Row Total 50 150 100 300 F (or withdrawal) Rating Excellent Average Poor Column Total 25 21 60 18 35 27 80 15 75 40 130 15 12 30