The authors of the article “Long-Term Effects of Cathodic Protection on Prestressed Concrete Structures” (Corrosion, 1997: 891–908) presented a scatter plot of permeation flux (mA/cm2

) versus foil thickness

(cm1

); the substantial linear pattern was used as a basis for an important conclusion about material behavior. The Minitab output from fitting the simple linear regression model to the data follows.

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. Does the model appear to be useful?

d. Predict flux when inverse thickness is 45 in a way that conveys information about precision and reliability.

e. Investigate model adequacy.