The alkalinity, in milligrams per liter, of water in the upp…
The alkalinity, in milligrams per liter, of water in the upper reaches of rivers in a particular region is known to be normally distributed with a standard deviation of 10 mg/l. Alkalinity readings in the lower reaches of rivers in the same region are also known to be normally distributed, but with a standard deviation of 25 mg/l. Ten alkalinity readings are made in the upper reaches of a river in the region and fifteen in the lower reaches of the same river with the following results. Upper reaches 91,75,91,88,94,63,86,77,71,69 Lower reaches 86,95,135,121,68,64,113,108,79,62,143,108,121,85,97 Investigate, at the 1% level of significance, the claim that the true mean alkalinity of water in the lower reaches of this river is greater than that in the upper reaches.