Average tuition for a master’s degree ranges from $30,000 at public universities to $40,000 at private schools. But a graduate degree can be a good investment. PayScale’s numbers for the median salary earned with its pick for the best five graduate degrees are master’s in biostatistics, $105,900; master’s in statistics, $113,700; Ph.D. in computer science, $147,400; Ph.D. in economics, $125,800; and a master’s in applied math, $124,900. The median salaries for PayScale’s five worst graduate degrees are $46,600 with a master’s of fine arts, $48,700 in early childhood education, $59,900 in divinity and elementary education, and $58,200 in reading and literacy.

a. Why do people with different graduate degrees have different salaries?

b. Draw a graph of the labor markets for Ph.D. economists and early childhood educators to illustrate your explanation of the differences in the salaries of these two groups.