A new method of planning an ecological network was presented in Landscape Ecology Engineering (Jan. 2013). The methodology protects linear green areas that act as ecological corridors for potential movement paths of wild animals (e.g., birds). This requires a prediction of the bird density in the green area. In a sample of 21 bird habitats in China, the researchers determined the bird density (number of birds per hectare) and the percentage of the habitat covered by vegetation (i.e., a green area). Data similar to the data reported in the journal article are listed in the table. The researchers used the data to fit the model, E(y) = β_o + β₁x where y = bird density and x = vegetation coverage (percentage).

a. Graph the points in a scatterplot. What type of linear relationship (positive or negative) appears to exist?

b. Fit the straight-line model to the data and obtain the least squares prediction equation.

c. Is there sufficient evidence to indicate that bird density increases linearly as percent vegetation coverage increases? Test using α = .01.

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BIRDDEN HABITAT DENSITY COVER (birds/hectare) (%) 1 0.3 2 0.25 2 3 2 4 1 6. 5 0.5 6. 10 7 3 12 8. 5 17 9 5 20 10 1 25 11 6. 30 12 5 37 13 8. 40 14 2 45 15 7 50 16 16 58 17 5 60 18 20 71 19 5 80 20 37 90 21 100