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) what is the mean service time from the 764 customers?
the mean service time from the 764 customers is □ seconds
(type an integer or a decimal. do not round)

Explanation:

Step1: Recall the formula for confidence interval

The formula for a confidence interval for the population mean \(\mu\) is \(\bar{x}-E<\mu <\bar{x} + E\), where \(\bar{x}\) is the sample mean and \(E\) is the margin of error. The mid - point of the confidence interval (lower bound \(L = 155.3\) and upper bound \(U=158.1\)) is the sample mean \(\bar{x}\). The formula for the sample mean \(\bar{x}=\frac{L + U}{2}\).

Step2: Calculate the sample mean

Substitute \(L = 155.3\) and \(U = 158.1\) into the formula \(\bar{x}=\frac{155.3+158.1}{2}\).

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Answer:

\(156.7\)