The variable 2013 Cost represents the four-year cost including tuition, supplies, room and board, the variable Annual

Question:

The variable "2013 Cost" represents the four-year cost including tuition, supplies, room and board, the variable "Annual ROI" represents the return on investment for graduates of the school-essentially how much you would earn on the investment of attending the school-the variable "Grad Rate" represents the graduation rate of the school.

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(a) In Problem 47 from Section 4.1, we saw that a scatter diagram between "2013 Cost" and "Grad Rate" treating "2013 Cost" as the explanatory variable suggested a positive association between the two variables. Treating "2013 Cost" as the explanatory variable, x, test whether a negative association exists between the 2013 cost and annual ROI for graduates of four-year schools at the α = 0.01 level of significance. Normal probability plots suggest the residuals

are normally distributed.

(b) Construct a 90% confidence interval for the slope of the true least-squares regression line.