The manager of a computer help desk operation in Moncton has collected enough data to conclude that the time per call is normally distributed with a mean equal to 8.21 minutes and a standard deviation of 2.14 minutes. The manager wants to set the time limit that only 8% of all calls will exceed this limit. The time limit should be
A) about 11.23 minutes.
B) about 5.25 minutes.
C) about 14.58 minutes.
D) about 10.35 minutes.
E) about 20.29 minutes.

Question

Quizplus · Accepted Answer

Given that the distribution of call times is normal with a mean of 8.21 minutes and a standard deviation of 2.14 minutes, and we want to find the time limit exceeded by only 8% of calls, we look for a z-score corresponding to the top 8% in a standard normal distribution. This z-score is approximately 1.41. Using the formula for a value in a normal distribution, X = μ + zσ, where μ is the mean, σ is the standard deviation, and z is the z-score, we calculate X = 8.21 + (1.41)(2.14) ≈ 11.23 minutes.

The Manager of a Computer Help Desk Operation in Moncton