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

question 14

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, $\mu$ , has changed from the 1990 mean of $9.4$ minutes? Perform the appropriate hypothesis test using a significance level of $0.01$ . Assume that $\sigma=4.2$ minutes.

• A) Since the P-value is greater than the significance level, the data provide sufficient evidence to accept the null hypothesis and conclude that the mean call duration has changed.
• B) Since the P-value is less than the significance level, the data provide sufficient evidence to reject the null hypothesis and conclude that the mean call duration has changed.
• C) Since the P-value is greater than the significance level, the data provide insufficient evidence to reject the null hypothesis and conclude that the mean call duration has changed.
• D) Since the P-value is greater than the significance level, the data provide sufficient evidence to reject the null hypothesis and conclude that the mean call duration has changed.

---

Definitions:

Missile

A guided weapon system designed to deliver a payload from a source to a target at high velocities.

Probability

A measure of how likely an event is to occur, ranging from 0 (impossible event) to 1 (certain event).

Union

An organized association of workers formed to protect and further their rights and interests; or, in mathematics, the set containing all the distinct elements of some given sets.

Dependent Events

Events where the outcome or occurrence of the first affects the outcome or occurrence of the second.