Exercise 14.5 showed an ANOVA for comparing mean customer satisfaction scores for three service centers. The sample means on a scale of 0 to 10 were 7.60 in San Jose, 7.80 in Toronto, and 7.10 in Bangalore. Each sample size = 100, MS error = 0.47, and the F test statistic = 27.6 has P-value < 0.001.
a. Explain why the margin of error for separate 95% confidence intervals is the same for comparing the population means for each pair of cities. Show that this margin of error is 0.19.
b. Find the 95% confidence interval for the difference in population means for each pair of service centers. Interpret.
c. The margin of error for Tukey 95% multiple comparison confidence intervals for comparing the service centers is 0.23. Construct the intervals. Interpret.
d. Why are the confidence intervals different in part b and in part c? What is an advantage of using the Tukey intervals?