The accompanying data was read from a graph that appeared in the article “Reactions on Painted Steel Under the Influence of Sodium Chloride, and Combinations Thereof”

(Ind. Engr. Chem. Prod. Res. Dev., 1985: 375–378). The independent variable is SO2 deposition rate (mg/m2

/d), and the dependent variable is steel weight loss (g/m2

).

a. Construct a scatter plot. Does the simple linear regression model appear to be reasonable in this situation?

b. Calculate the equation of the estimated regression line.

c. What percentage of observed variation in steel weight loss can be attributed to the model relationship in combination with variation in deposition rate?

d. Because the largest x value in the sample greatly exceeds the others, this observation may have been very influential in determining the equation of the estimated line. Delete this observation and recalculate the equation. Does the new equation appear to differ substantially from the original one (you might consider predicted values)?