In 1990, the average duration of long-distance telephone calls originating in on
ID: 3228682 • Letter: I
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 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, µ, is different from the 1990 mean of 9.4 minutes? Perform the appropriate hypothesis test using a significance level of 0.01. Assume that s = 4.8 minutes.
A. With a z of -1.2 there is sufficient evidence 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.
Explanation / Answer
The statistical software output for this problem is:
One sample Z hypothesis test:
: Mean of population
H0 : = 9.4
HA : 9.4
Standard deviation = 4.8
Hypothesis test results:
Hence,
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.
Option D is correct.
Mean n Sample Mean Std. Err. Z-Stat P-value 50 8.6 0.67882251 -1.1785113 0.2386Related Questions
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