Question 7.106

7.106 Average service time.

Recall the drive-thru study in Exercise 7.57 (page 395). Another benchmark that was measured was the service time. A summary of the results (in seconds) for two of the chains is shown here.

Chain
Taco Bell 308 158.03 35.7
McDonald’s 317 189.49 42.8
  1. Is there a difference in the average service time between these two chains? Test the null hypothesis that the chains’ average service time is the same. Use a significance level of 0.05.
  2. Construct a 95% confidence interval for the difference in average service time.
  3. Lex plans to go to Taco Bell and Sam to McDonald’s. Is it true that there is a 95% chance that the interval in part (b) contains the difference in their service times? Explain your answer.