Question 7

Acid rain is an environmental challenge in many places aroundthe world. It refers to rain or any other form of precipitationthat is unusually acidic, i.e. rainwater having elevated levels ofhydrogen ions (low pH). The measure of pH is a measure of theacidity or basicity of a solution and has a scale ranging from 0 to14. Distilled water, with carbon dioxide removed, has a neutral pHlevel of 7. Liquids with a pH less than 7 are acidic. However, evenunpolluted rainwater is slightly acidic with pH varying between 5.2to 6.0 due to the fact that carbon dioxide and water in the airreact together to form carbonic acid. Thus, rainwater is onlyconsidered acidic if the pH level is less than 5.2..

In a remote region of Algonquin Park, a biologist measured thepH levels of rainwater and obtained the following data for 16rainwater samples on 16 different lakes:

4.73	4.79	4.87	4.88
5.04	5.06	5.07	5.09
5.11	5.16	5.18	5.21
5.23	5.24	5.25	5.25

Is there reason to believe that the is considered acidic (lessthan 5.20)?

Use the Sign Test to test the claim at 95% confidence that therainwater from this region has a median pH level less than5.20.

a) State the Hypotheses (1)

b) State the decision rule (1)

c) Determine the test statistic (1)

d) State your decision and interpretation. (1,1)