A corporation administers an aptitude test to all new sales representatives. Management is interested in extent to which this test is capable to predict sales representatives' eventual success. The accompanying table records average weekly sales as well as aptitude test scores for the random sample of eight representatives.
Weekly Sales: 10, 12, 28, 24, 18, 16, 15, 12
Test Scores: 55, 60, 85, 75, 80, 85, 65, 60
a) Determine the linear regression of weekly sales on aptitude test scores.
b) Interpret the estimated slope of regression line.