Suppose life expectancy is normally distributed with mean 60 and variance 9. (Actually this must be an approximation but assume it is exact, just for simplicity.)
(a) For a randomly selected person, what is the probability of a life span greater than 62 years?
(b) For a group of 4 randomly selected people, what is the probability of an average life span greater than 62 years?
(c) For a group of 16 randomly selected people, what is the probability of an average life span greater than 62 years?