Posted by Jade on .
The accounting department at Weston Materials, Inc., a national manufacturer of unattached garages, reports that is takes two construction workers a mean of 32 hours and a standard deviation of 2 hours to erect the red barn model. Assume the assembly times follow the normal distribution.
a. Determine the Z values for 29 and 34 hours. What percent of the garages take between 32 hours and 34 hours to erect?
b. What percent of the garages take between 29 and 34 hours to erect?
c. What percent of the garages take 28.7 hours or less to erect?
d. Of the garages, 5 percent take how many hours or more to erect?

statistics 
PsyDAG,
Z = (xmean)/SD
Calculate the Z scores for the values above. Look them up in a table in the back of your stat text labeled something like "areas under the normal distribution." Find the proportions between or beyond the indicated values and convert to percentages.
I hope this helps.