The method of tree ring dating gave the following years A.D. for an archaeological excavation site. assume that the population ofxvalues has an approximately normal distribution.

1236 1236 1292 1299 1268 1316 1275 1317 1275

(a) using calculator with mean and standard deviation keys to what is the sample mean yearxand sample standard deviations.

x=

s=

(b) a 90% confidence interval for the mean of all tree ring dates from this archaeological site.

lower limit

upper limit