The age of a students in a class is a normal random variable.There are 80 students in our class. I select 9 students randomlyand calculate the mean of their ages (sample mean). I repeat thisexperiment 1,000,000 times. Then I calculate the mean and standarddeviation of the 1,000,000 sample means that I measured; thecalculated values are 22 and 4, respectively. What is theprobability that the age of a randomly selected student in theclass is below 20?
