posted by tony .
The average age of a vehicle registered in the United States is 8 years, or 96 months. Assume the standard deviation is 16 months. If a random sample of a group of 48 vehicles is selected find the probability that the mean of the group’s age is between 90 and 100 months.
Z = (score-mean)/SEm
SEm = SD/√n
Use same table indicated in previous post.