Question

the trade magazine qsr routinely checks the drive - through service times of fast - food restaurants. a 90% confidence interval that results from examining 764 customers in taco bells drive - through has a lower bound of 155.3 seconds and an upper bound of 158.1 seconds. complete parts (a) through (c)
(a) the mean service time from the 764 customers is 156.7 seconds
(type an integer or a decimal. do not round.)
(b) what is the margin of error for the confidence interval?
the margin of error is 1.4 seconds
(type an integer or a decimal. do not round.)
(c) interpret the confidence interval.
select the correct choice below and fill in the answer boxes to complete your choice
(type integers or decimals. do not round.)
a. one can be % confident that the mean drive - through service time of taco bell is seconds
b. there is a % probability that the mean drive - through service time of taco bell is between seconds and seconds
c. the mean drive - through service time of taco bell is seconds % of the time
d. one can be % confident that the mean drive - through service time of taco bell is between seconds and seconds

Explanation:

A confidence interval gives a range of values within which the population parameter (here, the mean drive - through service time) is likely to lie. A 90% confidence interval means that if we were to take many samples and construct confidence intervals in the same way, about 90% of those intervals would contain the true population parameter.

For part (c), option D is correct. The confidence level (90% in this case) is the percentage of confidence we have that the true population mean lies within the calculated interval (lower bound = 155.3 seconds and upper bound = 158.1 seconds).

Answer:

D. One can be 90% confident that the mean drive - through service time of Taco Bell is between 155.3 seconds and 158.1 seconds.