The manager of a computer help desk operation has collected enough data to conclude that the distribution of time per call is normally distributed with a mean equal to 8.21 minutes and a standard deviation of 2.14 minutes. The manager has decided to have a signal system attached to the phone so that after a certain period of time, a sound will occur on her employees' phone if she exceeds the time limit. The manager wants to set the time limit at a level such that it will sound on only 8 percent of all calls. The time limit should be:
A) 10.35 minutes.
B) approximately 5.19 minutes.
C) about 14.58 minutes.
D) about 11.23 minutes.

Question

Quizplus · Accepted Answer

To find the time limit that will sound on only 8 percent of all calls, we use the Z-score formula for a normal distribution. Given that we want the upper 8% (which corresponds to a Z-score of approximately 1.41 for the upper tail), we can calculate the time limit as follows: Time limit = mean + (Z-score * standard deviation) = 8.21 + (1.41 * 2.14) ≈ 11.23 minutes.

The Manager of a Computer Help Desk Operation Has Collected