Suppose the correlation between the average height of parents and the height of their firstborn male child is 0.5. You are also told that: 

• The average height of all parents is 66 inches.
• The standard deviation of the average height of parents is 4 inches.
• The average height of all male children is 70 inches.
• ‘The standard deviation of the height of all male children is 4 inches.

If a mother and father are 73 and 80 inches tall, respectively, how tall do you predict their son to be? Explain why this is called “regression toward the mean.”