Question: 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 straight-line pattern over time.
They reported that the least-squares regression line
pH = 5.43 - (0.0053 × weeks)
fit the data well.
(a) Draw a graph of this line. Is the association positive or negative? Explain in plain language what this association means.
(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.