Representative data read from a plot that appeared in the paper “Effect of Cattle Treading on Erosion from Hill Pasture: Modeling Concepts and Analysis of Rainfall Simulator Data” (Australian Journal of Soil Research [2002]: 963–977) on runoff sediment concentration for plots with varying amounts of grazing damage, measured by the percentage of bare ground in the plot, are given for gradually sloped plots and for steeply sloped plots.

Gradually Sloped Plots Bare ground (%) 5 10 15 25 Concentration 50 200 250 500 Bare ground (%) 30 40 Concentration 600 500 Steeply Sloped Plots Bare ground (%) 5 5 10 15 Concentration 100 250 300 600 Bare ground (%) 20 25 20 30 Concentration 500 500 900 800 Bare ground (%) 35 40 35 Concentration 1100 1200 1000

a. Using the data for steeply sloped plots, find the equation of the least-squares line for predicting y 5 runoff sediment concentration using x 5 percentage of bare ground. y^ 5 59.9 1 27.46x

b. What would you predict runoff sediment concentration to be for a steeply sloped plot with 18% bare ground?

c. Would you recommend using the least-squares equation from Part

(a) to predict runoff sediment concentration for gradually sloped plots? If so, explain why it would be appropriate to do so. If not, provide an alternative way to make such predictions.