The ability to determine the age of some individuals can be difficult if there are not quality government records of birth. Bone growth takes place at the growth plates at the end of long bones. Once all growth plates fuse, growth stops, and an individual is considered a biological adult. The age at which growth plates fuse for males is approximately normally distributed with a mean of 19 years and a standard deviation of 15.4 months.
(a) What is the probability a male’s growth plates fuse after age 20?
(b) What is the probability a male’s growth plates fuse before age 17?
(c) What proportion of a male’s growth plates fuse between 15 and 17 years of age?
(d) Would it be unusual for a male’s growth plates to fuse when he is 23 years old? Explain.