The state test scores for 12 randomly selected high school seniors are shown on the right. Complete parts (a) through (c) below. 1427 1227 980 698 722 835 Assume the population is normally distributed. 727 740 545 622 1449 946 (a) Find the sample mean. x = (Round to one decimal place as needed.) %3D (b) Find the sample standard deviation. %3= (Round to one decimal place as needed.) (c) Construct a 90% confidence interval for the population mean u. A 90% confidence interval for the population mean is ). (Round to one decimal place as needed.)