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Sample Z Test

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Directions:
Perform a one sample z test for a population mean using the p value approach. Be sure to state the hypothese and the significance leve, to compute the value of the test statistics, to obtain the p value and to state your conclusion.
Question:
In 1990, the average duration of long distance telephone calls originating in one town was 9.4 minutes. A long distance telephone company wants to preform a hypotheses test to determind whether the average duration of long distance phone calls has changed from the 1990 mean of 9.4 minutes. The mean duration for a ramdom sample of 50 calls originating in the town was 8.6 minutes. Do the data provide suggicient evidence to conclude that the mean call duration U, has changed from the 1990 mean of 9.4 minutes? Perform the appropriate hypothesis test using a signicance level of 0.20. Assume that sigma=4.8 minutes.