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.   Σ?=205 Σ(?−?̅)2=56.43 a) Calculate the sample mean, ?̅. 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.

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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.

 

Σ?=205 Σ(?−?̅)2=56.43

  1. a) Calculate the sample mean, ?̅.
  1. b) Calculate the sample standard deviation
  2. 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. 

 

 

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