15.34 An instructor in an economics class is considering three different texts. He is also considering three types of examinations—multiple choice, essay, and a mix of multiple choice and essay questions. During the year he teaches nine sections of the course and randomly assigns a text–examination type combination of each section. At the end of the course he obtained students’

evaluations for each section. These ratings are shown in the accompanying table.

Text Examination A B C Multiple choice 4.8 5.3 4.9 Essays 4.6 5.0 4.3 Mix 4.6 5.1 4.8

a. Prepare the analysis of variance table.

b. Test the null hypothesis of equality of population mean ratings for the three texts.

c. Test the null hypothesis of equality of population mean ratings for the three examination types.