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. 1229 1271 1229 1215...

(a) Use a calculator with mean and standard deviation keys to find the sample mean year x and sample standard deviations. (Round your answers to the nearest whole number.)

x =
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
upper limit