8.54 Hotel Costs Refer to Exercise 8.19. The means and standard deviations for 50 billing statements from each of the computer databases of each of the three hotel chains are given in the table:

a. Find a 95% confidence interval for the difference in the average room rates for the Marriott and the Doubletree hotel chains.

b. Find a 99% confidence interval for the difference in the average room rates for the Westin and the Doubletree hotel chains.

c. Do the intervals in parts a and b contain the value (1 2) 0? Why is this of interest to the researcher?

d. Do the data indicate a difference in the average room rates between the Marriott and the Doubletree chains? Between the Westin and the Doubletree chains?

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Marriott Westin Doubletree Sample average ($) 150 165 125 Sample standard deviation 17.2 22.5 12.8