4. Interval estimation of a population mean, population standard deviation unknown The Business Environment and Enterprise Performance Survey (BEEPS), developed by the European Bank for Reconstruction and Development and the World Bank, is a survey of more than 4,000 firms in 22 transition countries. Conducted in 2000, BEEPS gathered information on the impediments to business growth in transition countries. As part of BEEPS, firms that import goods answered the question, "How many days does it take from the time your goods arrive in their port of entry until the time you can claim them from customs?" For the sample of 35 importing firms in Armenia, the sample mean X was 8.3 days, and the sample standard deviation s was 9.9 days.You are 95% confident that the mean wait time for imported goods to clear customs in Armenia is between LCL = 7 and UCL = days