Three teaching methods were tested on a group of 18 students with homogeneous backgrounds in statistics and comparable aptitudes. Each student was randomly assigned to a method and at the end of a...

Three teaching methods were tested on a group of 18 students with homogeneous backgrounds in statistics and comparable aptitudes. Each student was randomly assigned to a method and at the end of a 6-week program was given a standardized exam. Because of classroom space, the students were not equally allocated to each method. The results are shown in Table 14.13.

(a) Test for a difference in distributions of test scores for the different teaching methods using the KruskalWallis test.

(b) If there are differences, explain the differences using a multiple comparison test.