Assume the population is normally distributed. (a) Find the sample mean. x = 909.7 (Round to one decimal place as needed.) (b) Find the sample standard deviation. s 304.4 (Round to one decimal place as needed.) (c) Construct a 99% confidence interval for the population mean µ. A 99% confidence interval for the population mean is ( (Round to one decimal place as needed.) View an example Get more help .​