Archaeology: Tree Rings Tree-ring dating from archaeological excavation sites is used in conjunction with other chronologic evidence to estimate occupation dates of prehistoric Indian ruins in the southwestern United States. It is thought that Burnt Mesa Pueblo was occupied around 1300 a.d. (based on evidence from potsherds and stone tools). The following data give tree-ring dates (a.d.) from adjacent archaeological sites (Bandelier Archaeological Excavation Project: Summer 1990 Excavations at Burnt Mesa Pueblo, edited by T. Kohler, Washington State University Department of Anthropology, 1992):

1189 1267 1268 1275 1275 1271 1272 1316 1317 1230 i. Use a calculator with mean and standard deviation keys to verify that x 5 1268 and s < 37.29 years.

ii. Assuming the tree-ring dates in this excavation area follow a distribution that is approximately normal, does this information indicate that the population mean of tree-ring dates in the area is different from (either higher or lower than) that in 1300 a.d.? Use a 1% level of signifi cance.