statistic
posted by Coco .
The time necessary to assemble a discount store display is normally distributed with μ = 5 minutes and σ = 30 seconds. A large number of potential employees are timed assembling a practice display. How much time (in minutes) should the personnel manager allow the potential employees to assemble the display if the store wants only 80% of the people to complete the task?

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion (.80) related to the Z score. Use the Z score in the equation below.
Z = (scoremean)/SD