Acid rain. Researchers studying acid rain measured the acidity of precipitation in a Colorado wilderness area for 150 consecutive weeks. Acidity is measured by pH. Lower pH values show higher acidity. The acid rain researchers observed a linear pattern over time. They reported that the least-squares regression line fit the data well:

pH = 5.43 − (0.0053 x weeks)

A.) Is the association positive or negative? Explain in plain language what this regression is telling us.

B.) According to the regression line, what was the pH at the beginning of the study (weeks = 1)? At the end (weeks = 150)?

C.) What is the slope of the regression line? Explain clearly what this slope says about the change in the pH of the precipitation in this wilderness area. Does the slope have units? What are they?