A manufacturer of paint used for marking road surfaces developed a new formulation that needs to be tested for durability. One question concerns the concentration of pigment in the paint. If the concentration is too low, the paint will fade quickly; if the concentration is too high, the paint will not adhere well to the road surface. The manufacturer applies paint at various concentrations to sample road surfaces and obtains a durability measurement for each sample.

a. Have your computer program calculate a regression equation with durability ­predicted by concentration. Interpret the slope coefficient.
b. Find the coefficient of determination. What does it indicate about the predictive value of concentration?

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Conc. 20 20 20 20 20 20 20 20 20 2020 20 Durab. 533 252 49 20.3 55.5 50.7 57.1 34 52.7 42.5 51.7 47.0 Conc. 30 30 30 30 30 30 30 330 30 30 30 Durab. 67.2 66.7 56.7 60.3 68.0 56. 59.9 63.3 64.4 49.3 61.7 62.3 Conc. 40 40 40 40 40 40 40 40 40 40 4040 Durab 64.7 68,0 76.5 69.9 691 50.7 571 65.7 67. 744 73.5 69.9 Conc. 50 50 50 5050 50 50 50 50 5050 Durab. 516 75.7 55.9 76 55.3 73.3 615 53.3 74473.6 76.5 73.3 Conc 60 60 06060 60 60 6060 60 60 60 Durab. 58.7 705 52.5 59.9 65.9 63.3 64.9 53.6 52.5 63.8 59.7 58.9