19. The following data is representative of that reported in the article An Experimental Correlation of Oxides of Nitrogen Emissions from Power Boilers Based on Field Data (J. Engrg. Power, July 1973: 165—170), with x  burner area liberation rate (MBtu/hr-ft2) and y  NOx emission rate (ppm):

x 100 125 125 150 150 200 200 y 150 140 180 210 190 320 280 x 250 250 300 300 350 400 400 y 400 430 440 390 600 610 670

a. Assuming that the simple linear regression model is valid, obtain the least squares estimate of the true regression line.

b. What is the estimate of expected NOx emission rate when burner area liberation rate equals 225?

c. Estimate the amount by which you expect NOx emission rate to change when burner area liberation rate is decreased by 50.

d. Would you use the estimated regression line to predict emission rate for a liberation rate of 500?

Why or why not?

e. Does the simple linear regression model appear to do an effective job of explaining variation in emission rate? Justify your assertion.