Posted by Coco on .
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?

statistic 
PsyDAG,
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