A clinic offers a weight-loss program. The table below gives the amounts of weight loss, in pounds, for a random sample of 20 of its clients at the conclusion of the program. Assume that the data are normally distributed. Complete parts (a) and (b). 17 14 11 20 15 18 12 24 25 19 7 15 12 18 17 9 17 15 25 a. Find a 90% confidence interval for the population mean The 90% confidence interval is from a lower limit of | | to an upper limit of (Round to two decimal places as needed.) For a random sample of 400 students, the mean cost for textbooks during the first semester of college was found to be $362.75, and the sample standard deviation was $38.89. Assuming that the population is normally distributed, find the margin of error of a 30% confidence interval for the population mean. The margin of error for an 80% confidence interval is (Round to two decimal places as needed.)