The article “Effects of Gamma Radiation on Juvenile and Mature Cuttings of Quaking Aspen” (Forest Science, 1967:

240–245) reports the following data on exposure time to radiation (x, in kr/16 hr) and dry weight of roots (y, in mg  101

).

a. Construct a scatter plot. Does the plot suggest that a linear probabilistic relationship is appropriate?

b. A linear regression results in the least squares line y

127  6.65x, with s
16.94. Compute the residuals and standardized residuals and then construct residual plots.

What do these plots suggest? What type of function should provide a better fit to the data than a straight line does?