A marketing survey involves product recognition in New York and California. Of 558 New Yorkers surveyed, 193 knew the product while 196 out of 614 Californians knew the product. Construct a 99% confidence interval for the difference between the two population proportions.

The concentration of hexane (a common solvent) was measured in units of micrograms per liter for a simple random sample of fourteen specimens of untreated ground water taken near a municipal landfill. The sample mean was 241.8 with a sample standard deviation of 8.8. Ten specimens of treated ground water had an average hexane concentration of 149.5 with a standard deviation of 7.4. It is reasonable to assume that both samples come from populations that are approximately normal. Construct a 95% confidence interval for the reduction of hexane concentration after treatment.