In 1990, the Average Duration of Long-Distance Telephone Calls Originating $9.4$

Multiple Choice

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 perform a hypothesis test to determine whether the average duration of long-distance phone calls has changed from the 1990 mean of $9.4$ minutes. The mean duration for a random sample of 50 calls originating in the town was $8.6$ minutes. Does the data provide sufficient evidence to conclude that the mean call duration, $\mu$ , is different from the 1990 mean of $9.4$ minutes? Perform the appropriate hypothesis test using a significance level of $0.01$ . Assume that $\sigma=4.8$ minutes.

A) With a $z$ of $-1.2$ there is sufficient eridence to conclude that the mean value has changed from the 1990 mean of $9.4$ minutes.
B) With a P-value of $0.2302$ there is not sufficient evidence to conclude that the mean value is less than the 1990 mean of $9.4$ minutes.
C) With a P-value of $0.2302$ there is sufficient evidence to conclude that the mean value is less than the 1990 mean of $9.4$ minutes.
D) With a $z$ of $-1.2$ there is not sufficient evidence to conclude that the mean value has changed from the 1990 mean of $9.4$ minutes.