The values of COD for the paper mill in Exercise 5 are shown in Table 4.6. The state requires that the mill show that the population mean for its effluent be less than 500 mg/L. Is there evidence that...

The values of COD for the paper mill in Exercise 5 are shown in Table 4.6. The state requires that the mill show that the population mean for its effluent be less than 500 mg/L. Is there evidence that the mean value is less than this standard, using α = 5%?

Exercise 5

Chemical Oxygen Demand (COD) is a common measure of organic pollutants in groundwater. A state environmental agency sets a standard that a certain paper mill must demonstrate that its effluent has a probability less than 20% of having high COD. Inspectors will collect water specimens at 30 randomly selected dates and analyze each for high COD.

(a) Will this sample be large enough to meet the requirements of the large sample test for proportions?

(b) Of the 30 specimens, 5 have a high COD. At α = 5%, what should the agency conclude?

(c) After the mill installs a new coagulation system for its wastewater, the agency collects another 30 specimens. They find that only 1 has high COD. At α = 5%, what should the agency conclude?