71. 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. Testing Eval., 1987: 333—336). The variables are x  oxide-layer thickness (mm) and y  eddy-current response (arbitrary units).

x 0 7 17 114 133 y 20.3 19.8 19.5 15.9 15.1 x 142 190 218 237 285 y 14.7 11.9 11.5 8.3 6.6

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.