In 2002, a Census Bureau survey reported that the mean total earnings that a full-time worker in the United States can expect to earn between ages 25 and 64 is $1.2 million for those with only a high-school education and $2.1 million for those with a college degree but no advanced degree.
a. Assuming four years for a college degree and a straight-line regression of y = total earnings on x = number years of education, what is the slope? Interpret it.
b. If y instead measures earnings per year (rather than for 40 years), then what is the slope? Interpret.