An electric utility is interested in developing a model relating peak hour demand (y in kilowatts) to total monthly energy usage during the month (x, in kilowatt hours). Data for 50 residential customers are shown in the following table.
(a) Draw a scatter diagram of y versus x.
(b) Fit the simple linear regression model.
(c) Test for significance of regression using a = 0.05.
(d) Plot the residuals versus yi and comment on the underlying regression assumptions. Specifically, does it seem that the equality of variance assumption is satisfied?
(e) Find a simple linear regression model using √y as the response. Does this transformation on y stabilize the inequality of variance problem noted in part (d) above?

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Customer Customer 0.31 679 0.79 26 1434 0.44 292 27 837 4.20 1748 1012 0.56 28 4.88 29 1381 493 0.79 3.48 582 2.70 30 7.58 1428 31 1156 3.64 2.63 6. 1255 997 4.73 32 1777 4.99 2189 9.50 33 370 0.59 1097 5.34 34 2316 8.19 9. 10 2078 6.85 35 1130 4.79 1818 5.84 36 0.51 11 463 1700 12 5.21 37 770 1.74 13 747 3.25 38 724 4.10 2030 4.43 39 808 3.94 14 1643 15 3.16 40 790 0.96 783 16 414 0.50 41 3.29 17 354 0.17 42 406 0.44 3.24 18 1276 1.88 43 1242 19 745 0.77 44 658 2.14 795 20 3.70 45 1746 5.71 4.12 21 540 0.56 46 895 1.56 22 874 47 1114 1.90 23 1543 5.28 48 413 0.51 24 1029 0.64 49 1787 8.33 4.00 25 710 50 3560 14.94