Question

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−𝑥̅)²=56.43 a) Calculate the sample mean, 𝑥̅. [2] 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

          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−𝑥̅)²=56.43
a) Calculate the sample mean, 𝑥̅. [2]
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

Added by Brian G.

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