Alkalinity of river water. In Exercise 5.129

(p. 303), you learned that the mean alkalinity level of water specimens collected from the Han River in Seoul, South Korea, is 50 milligrams per liter (Environmental Science

& Engineering, Sept. 1, 2000). Consider a random sample of 100 water specimens collected from a tributary of the Han River. Suppose the mean and standard deviation of the alkalinity levels for the sample are, respectively, x = 67.8 mpl and s = 14.4 mpl. Is there sufficient evidence (at a = .01) to indicate that the population mean alkalinity level of water in the tributary exceeds 50 mpl?