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.

1257

1257

1292

1306

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 =	A.D.
s =	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	A.D.
upper limit	A.D.

Answer 1

a)

= X / n = 1285

S = sqrt [ (Xi - )² / n-1 ] = 24

b)

t critical value at 0.10 significance level with 8 df = 1.860

90% confidence interval for is

- t * S / sqrt(n) < < + t * S / sqrt(n)

1285 - 1.860 * 24 / sqrt(9) < < 1285 + 1.860 * 24 / sqrt(9)

1270.12 < < 1299.88

Lower limit = 1270

Upper limit = 1300