Chapter 12.1, Problem 19E

For Exercises 7 through 20, assume that all variables are normally distributed, that the samples are independent, that the population variances are equal, and that the samples are simple random samples, one front each of the populations. Also, for each exercise, perform the following steps.

a. State the hypotheses and identify the claim.

b. Find the critical value.

c. Compute the test value.

d. Make the decision.

e. Summarize the results, and explain where the differences in the means are.

Use the traditional method of hypothesis testing unless otherwise specified.

19. Number of Pupils in a Class A large school district has several middle schools. Three schools were randomly chosen, and four classes were selected from each. The numbers of pupils in each class are shown here. At a = 0.10, is there sufficient evidence that the mean number of students per class differs among schools?

MS 1	MS 2	MS 3
21	28	25
25	22	20
19	25	23
17	30	22