In 2015, the average duration of long- distance telephone calls from a certain town was 3.9 minutes. A telephone company wants to perform a test to determine whether this average duration of long-...

Please answer the questions attached

Extracted text: In 2015, the average duration of long- distance telephone calls from a certain town was 3.9 minutes. A telephone company wants to perform a test to determine whether this average duration of long- distance calls has changed. Fifty calls, originating from the town, was randomly selected and the following summary minutes. Σx= 205 Σ(x - ): 56.43 %3D a. Calculate the sample mean, x. b. Calculate the sample standard deviation c. Using the p value approach at the 1% level of significance, test whether the mean duration of long-distance calls from the town had increased. d. Construct the 99% confidence interval for the population mean duration of the long-distance calls from the town.


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