78. According to data from the Organization for Economic Cooperation and Development, the average U.S. worker takes 16 days of vacation each year (The Wall Street Journal, June 20, 2007). Assume that these data were based on a sample of 225 workers and that the sample standard deviation is 12 days. a. Construct the 95% confidence interval for the population mean. b. At the 95% confidence level, can we conclude that the average U.S. worker does not take 14 days of vacation each year?