Understanding Basic Statistics 6th Edition by Charles Henry Brase,Corrinne Pellillo Brase

Exercise 109

Normal Curve: Tree Rings Tree-ring dates were used extensively in archaeological studies at Burnt Mesa Pueblo (Bandelier Archaeological Excavation Project: Summer 1989 Excavations at Burnt Mesa Pueblo, edited by Kohler Washington State University Department of Anthropology). At one site on the mesa, tree-ring dates (for many samples) gave a mean date of 1 = year 1272 with standard deviation 1 = 35 years, At a second, removed site, the tree-ring dates gave a mean of 2 = year 1122 with standard deviation 2 = 40 years. Assume that both sites had dates that were approximately normally distributed. In the first area, an object was found and dated as x 1 = year 1250. In the second area, another object was found and dated as x 2 = year 1234.
(a) Convert both x 1 and x 2 to z values, and locate both of these values under the standard normal curve of Figure 7-12.
(b) Interpretation Which of these two items is the more unusual as an archaeological find in its location