Question

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.

1215 1222 1320 1180 1268 1316 1275 1317 1275

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

x =

Incorrect: Your answer is incorrect.

A.D.

s =

Incorrect: Your answer is incorrect.

yr

(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

Incorrect: Your answer is incorrect.

A.D.

upper limit

Incorrect: Your answer is incorrect.

A.D

Answer 1

Solution: Given that values : 1215 1222 1320 1180 1268 1316 1275 1317 1275

(a)

X = sum of terms/number of terms = 11388/9 = 1265.3333 = 1265

s = 50.1398 = 50

(b) n = 9, df = 8, 90% confidence level for t = 1.860

90% confidence interval for the mean of all tree = X +/- t*s/sqrt(n)
= 1265 +/- 1.86*50/sqrt(9)
= 1234 , 1296
Lower limit = 1234

upper limit = 1296