5.33 Some types of algae have the potential to cause damage to river ecosystems. The accompanying data on algae colony density (y) and rock surface area (x)

for nine rivers is a subset of data that appeared in a scatterplot in a paper in the journal Aquatic Ecology

(2010: 33–40).

x 50 55 50 79 44 37 70 45 49 y 152 48 22 35 38 171 13 185 25

a. Compute the equation of the least-squares regression line.

b. What is the value of r2 for this data set? Write a sentence interpreting this value in context. (Hint:

See Example 5.12.)

c. What is the value of se for this data set? Write a sentence interpreting this value in context. (Hint:

See Example 5.13.)

d. Is the linear relationship between rock surface area and algae colony density positive or negative? Is it weak, moderate, or strong? Justify your answer.