Posted by renea on Sunday, March 17, 2013 at 5:37pm.
The mean of nonresidential buildings is 30 years and the standard deviation of the ages of the buildings is 5 years. Determine the probability that a random sample of a group of 50 nonresidential buildings will have a mean age of less than 27.5 years.

stats  PsyDAG, Monday, March 18, 2013 at 12:36pm
Z = (scoremean)/SEm
SEm = SD/√n
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.