Question: Ecologists sometimes find strange relationships in the environment. One study seems to show that beavers benefit beetles. The researchers laid out 23 circular plots, each 4 meters in diameter, in an area where beavers were cutting down cottonwood trees. In each plot they counted the number of stumps from trees cut by beavers and the number of clusters of beetle larvae. The data are below.

a) Make a scatter plot that shows how the number of beaver-caused stumps influences the number of beetle larvae clusters. What does the plot show? (Ecologists think that the new sprouts from stumps are more tender than other cottonwood growth, so that beetles prefer them).

b) Find the least-squares regression line and draw it on your plot.

c) What percent of the observed variation in beetle larvae counts can be explained by straight-line dependence on stump counts? (It is suggested that SPSS be used to solve this problem)