The average annual age of doctors in a certain hospital is 44.0 years old with a standard deviation of 4.0 years. Assume that the variable is normally distributed.
(a) Find the probability that the age of a randomly selected doctor is less than 44.32 years.
(b) Find the probability that the mean age of a sample of 25 randomly selected doctors is less than 44.32 years.
(c): Why is there a difference in the two answers?