The environmental protection agency (epa) has collected data on lc50 measurements (concentrations that kill 50% of test animals) for certain chemicals likelyto be found in freshwater rivers and lakes. for certain species of fish, the lc50 measurements (in parts per million) for ddt in 12 experiments were as follows: 16,5,21,19,10,5,8,2,7,2,4,9 assume that the lc50 measurements have an approximately normal distribution. construct a 95% confidence interval for the true mean lc50 for ddt.