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Vanyuwa [196]
3 years ago
14

Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers. According

ly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes. Assume that the population standard deviation is 4 minutes. The 90% confidence interval for the population mean of waiting times is ________.
Mathematics
1 answer:
77julia77 [94]3 years ago
8 0

Answer: (14.18, 15.08)

Step-by-step explanation:

Given : Sample size : n= 64

Sample mean : \overline{x}=15

Standard deviation : \sigma=4

Significance level : \alpha: 1-0.90=0.1

Critical value : z_{\alpha/2}=1.645

The confidence interval for population mean is given by :-

\overline{x}\pm\ z_{\alpha/2}\dfrac{\sigma}{\sqrt{n}}\\\\=15\pm(1.645)\dfrac{4}{\sqrt{64}}\\\\\approx15\pm0.82\\\\=(14.18,\ 15.08)

Hence, the 90% confidence interval for the population mean of waiting times is (14.18, 15.08).

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