Use the computer output given in Exercise 9 of the previous section to decide whether the simple linear regression model specifies a useful relationship between flux and inverse foil thickness.

Exercise 9

The authors of the article “Long-Term Effects of Cathodic Protection on Prestressed Concrete Structures” (Corrosion, 1997: 891–908) presented a scatterplot of y steady-state permeation flux (‑Aycm2 ) versus x inverse foil thickness (cm21 ); the substantial linear pattern was used as a basis for an important conclusion about material behavior. This is the Minitab output from fitting the simple linear regression model to the data.

a. Interpret the estimated slope and the coefficient of determination.

b. Calculate a point estimate of true average flux when inverse foil thickness is 23.5.

c. Predict the value of flux that would result from a single observation made when inverse foil thickness is 45.

d. Verify that the sum of the residuals is zero and that squaring and summing the residuals results in the value of SSResid given in the output.