The figure at the top of the page is based on data from the article “Root and Shoot Competition Intensity Along a Soil Depth Gradient” (Ecology [1995]:

673– 682). It shows the relationship between aboveground biomass and soil depth within the experimental plots. The relationship is described by the estimated regression equation: biomass 529.85 1 25.29(soil depth)

and r 2 5 .65; P , 0.001; n 5 55. Do you think the simple linear regression model is appropriate here? Explain. What would you expect to see in a plot of the standardized residuals versus x?