statistics
posted by Sarah 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?
a.4.86
b.5.0
c.5.42
d.5.89

Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion (.8) in the largest portion and use the Z score to calculate the raw time (score). Don't forget to change to common units.