A company's quality manager wants to estimate, with a probability of 0.90, the copper content in a mixture to within 4%.
(a) How many samples must be selected if no prior information is available on the proportion of copper in the mixture?
(b) Suppose that the manager has made some changes in the process and wishes to determine if the copper content exceeds 15%. The manager would like to detect increases of 2% or more, with a probability of 0.98. How large a sample should be selected for a chosen level of significance of 2%?