The mean incubation time of fertilized chicken eggs kept at 100.5°F in a still-air incubator is 21 days. Suppose that the incubation times are approximately normally distributed with a standard deviation of 1 day. Source: University of Illinois Extension
(a) What is the probability that a randomly selected fertilized chicken egg hatches in less than 20 days?
(b) What is the probability that a randomly selected fertilized chicken egg takes over 22 days to hatch?
(c) What is the probability that a randomly selected fertilized chicken egg hatches between 19 and 21 days?
(d) Would it be unusual for an egg to hatch in less than 18 days? Why?