6.2 Multiple-choice exams. A researcher was interested in whether the order of the answers to multiple-choice questions affects exam scores. He made three versions of an exam. Each version had the same questions and the same set of answers, but the order of the possible answers was different for each version. The three versions were given to students in two classes having different instructors. Each class had an enrollment of 75 students. The researcher was concerned that scores might also depend on instructor, so instructor was treated as a blocking variable. Use a diagram to outline a block design for this experiment. Use Figure 6.2 as a model.