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.

1299

1313

1257

1243

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

The statistic software output for this problem is:

(a)

x = 1285 A.D.

s = 27.39 = 27 yr

(b)

Lower limit = 1268 A.D.

Upper limit = 1302 A.D.

(b)

t _/2,df = 1.833

Margin of error = E = t_/2,df * (s /n)

= 1.833 * (27.39 / 9)

Margin of error = E = 16.7

The 90% confidence interval estimate of the population mean is,

- E < < + E

1284.8 - 16.7 < < 1284.8 + 16.7

1268 < < 1302

L L = 1268

U L = 1302