Measuring water quality. Biochemical oxygen demand (BOD) measures organic pollutants in water by determining the amount of oxygen consumed by the microorganism which break down these compounds. BOD is hard to determine accurately. Total organic carbon (TOC) is easy to evaluate, so it is common to determine TOC and use regression to predict BOD. A typical regression equation for water entering municipal treatment plant is BOD = -55.43 + 1.507 TOC
Both BOD and TOC are measured in milligrams per liter of water.
(a) What does the slope of this line say about the relationship between BOD and TOC?
(b) What is the predicted BOD when TOC=0? Values of BOD less than 0 are impossible. Why do you think the prediction gives an impossible value?