The data in the table show the average earnings of year-round full-time workers by gender for several different levels of educational attainment.
Average Annual Earnings
Males _____________________ Females__
$21,659 ........................... $17,023
26,277 ............................ 19,162
35,725 ............................ 26,029
41,875 ............................ 30,816
44,404 ............................ 33,481
57,220 ............................ 41,681
71,530 ............................ 51,316
82,401 ............................ 68,875
(a) Use linear regression to find the linear equation that is the best for these data, with x representing the earnings for males and y representing the earnings for females.
(b) Find and interpret the slope of the linear regression line.
(c) If you made a similar linear model with data from 1965, how do you think its slope would compare with the slope found in part (b)? Explain.