-/0.3 Points] DETAILS BBUNDERSTAT12 7.2.013.S. MY NOTES ASK YOUR TEACHER PRACTICE A The method of tree ring dating gave the following years A.D. for an archaeological excavation site. Assume that the population of x values has an approximately normal distribution. 1,278 1,306 1,250 1,222 1,268 1,316 1,275 1,317 1,275 LO USE SALT (a) Use a calculator with mean and standard deviation keys to find the sample mean year x and sample standard deviation s. (Round your answers to four decimal places.) X 11 A.D. S = (b) Find a 90% confidence interval for the mean of all tree ring dates from this archaeological site. (Round your answers to the nearest whole number.) lower limit A.D. upper limit A.D. Need Help? Read It Watch It Submit