1)    The average age of doctors in a certain hospital is 48.0 years old. Suppose the distribution of ages is normal and has a standard deviation of 6.0 years. If 9 doctors are chosen at random for a committee, find the probability that the average age of those doctors is less than 48.8 years.
2) The length of country and western songs is normally distributed and has a mean of 170 seconds and a standard deviation of 40 seconds. Find the probability that a random selection of 16 songs will have mean length of more than 158.30 seconds.
3) The National Association of Realtors estimates that 23% of all homes purchased in 2004 were considered investment properties. If a sample of 900 homes sold in 2004 is obtained, what is the probability that fewer than 200 homes are going to be used as investment property?
4) A union official wanted to estimate the mean hourly wage of its members. A random
sample of 100 members gave a mean of $18.30 and standard deviation of $3.