The Wilson Company uses a great deal of water in the process of making industrial milling equipment. To comply with the federal clean water laws, it has a water purification system that all wastewater goes through before being discharged into a settling pond on the company’s property. To determine whether the company is complying with the federal requirements, sample measures are taken every so often. One requirement is that the average pH levels not exceed 7.4. A sample of 95 pH measures has been taken. The data for these measures are shown in a file called Wilson Water.
a. Considering the requirement for pH level, state the appropriate null and alternative hypotheses. Discuss why it is appropriate to form the hypotheses with the federal standard as the alternative hypothesis.
b. Based on the sample data of pH level, what should the company conclude about its current status on meeting the federal requirement? Test the hypothesis at the 0.05 level. Discuss your results in a memo to the company’s environmental relations manager.