Contaminated water: The concentration of benzene was measured in units of milligrams per liter for a simple random sample of five specimens of untreated wastewater produced at a gas field. The sample mean was
7.5
with a sample standard deviation of 1.7. Seven specimens of treated wastewater had an average benzene concentration of
3.3
with a standard deviation of
1.6
. It is reasonable to assume that both samples come from populations that are approximately normal, Construct an
80%
confidence interval for the reduction in benzene concentration after treatment, Use the TI-84 calculator and round the answers to one decimal place. An
80%
confidence interval for the reduction in benzerie concentration after treatment is