The data below on runoff sediment concentration for plots with varying amounts of grazing damage are representative values from a graph in the paper €œEffect of Cattle Treading on Erosion from Hill Pasture: Modeling Concepts and Analysis of Rainfall Simulator Data€(Australian Journal of Soil Research [ 2002]: 963€“ 977). Damage was measured by the percentage of bare ground in the plot. Data are given for gradually sloped and for steeply sloped plots.

a. Using the data for steeply sloped plots, find the equation of the least squares regression line for predicting y = runoff sediment concentration using x = percentage of bare ground.
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 regression line from Part (a) to predict runoff sediment concentration for gradually sloped plots? Explain.

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