Wear resistance of certain nuclear reactor components made of Zircaloy-2 is partly determined by properties of the oxide layer. The following data appears in an article that proposed a new nondestructive testing method to monitor thickness of the layer (“Monitoring of Oxide Layer Thickness on Zircaloy-2 by the Eddy Current Test Method,” J. of Testing and Eval., 1987: 333–336). The variables are x
oxide-layer thickness

( m) and y
eddy-current response (arbitrary units).

a. The authors summarized the relationship by giving the equation of the least squares line as y
20.6  .047x.

Calculate and plot the residuals against x and then comment on the appropriateness of the simple linear regression model.

b. Use s
.7921 to calculate the standardized residuals from a simple linear regression. Construct a standardized residual plot and comment. Also construct a normal probability plot and comment.