MY NOTES RS720THER 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 1,222 1.215 1,222 1.250 1.260 1.316 1,275 1,317 1,275 distribution. 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.) A.D. (b) When finding an 90% confidence interval, what is the critical value for confidence level? (Give your answer to three duimal places.) What is the maximal margin of error when finding a 90% confidence interval for the mean of all tree-ring dates from this archaeological site? (Round your answer to the nearest whole number.) E- 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 upper limit A.D. A.D.