Square root of the area ?
Given a table below which gives the years in A.D. for an archaeological excavation site using the method of tree ring dating:

Part A:
The sample mean is given by:

Therefore, the sample mean is 1268.
Part B:
We calculate the sample standard deviation as follows:

Part C:
The 90% confidence interval is given by:
Step-by-step explanation:
1.
(chain rule)
2 

C= 615.44
c=3.14(r)^2
c=3.14(14)^2