A trade magazine routinely checks the drive-through service times of fast-food restaurants. Upper A 90 % confidence interval that results from examining 624 customers in one fast-food chain's drive-through has a lower bound of 166.6 seconds and an upper bound of 170.0 seconds. What does this mean?

A.

One can be 90 % confident that the mean drive-through service time of this fast-food chain is between 166.6 seconds and 170.0 seconds.

B.

The mean drive-through service time of this fast-food chain is 168.3 seconds 90 % of the time.

C.

One can be 90 % confident that the mean drive-through service time of this fast-food chain is 168.3 seconds.

D.

There is a 90 % probability that the mean drive-through service time of this fast-food chain is between 166.6 seconds and 170.0 seconds.

The right answer is: A. "One can be 90 % confident that the mean drive-through service time of this fast-food chain is between 166.6 seconds and 170.0 seconds."

Step-by-step explanation:

We have a 90% confidence interval for the service-time that has a lower bound of 166.6 seconds and an upper bound of 170.0 seconds.

The intention when a confidence interval is calculated is to estimate, with the desired degree of confidence (in this case, 90%) a certain parameter of the population (in this case, the mean time) with only the information given by the sample.

The confidence interval does not give information about the probabilities of individual values or sample means, as is only an estimation calculated from a unique sample.

The right answer is: A. "One can be 90 % confident that the mean drive-through service time of this fast-food chain is between 166.6 seconds and 170.0 seconds."