# (20 pts)2. According to records, the average length of all long-distance calls placed in 1999 was...

###### Question:

(20 pts)2. According to records, the average length of all long-distance calls placed in 1999 was 12.44 minutes. The company's management wanted to check if the mean length of the current long-distance calls is different from 12.44 minutes. A sample of 150 produced a mean length of 13.71minutes with a standard deviation of 2.65 minutes. Using the 5% significance level, can you conclude that the mean length of all current long-distance calls is different from 12.44 minutes? a. State the null and alternative hypotheses. b. Construct a statistic to test the hypotheses and select the distribution to use. c. Find the critical value, and determine the rejection and non-rejection regions for this statistic. d. Make the decision and interpret.

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