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 1299 1222 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

using excel>addin>phstat>confidence interval>one sample with unknown sigma

we have

Confidence Interval Estimate for the Mean
Data
Sample Standard Deviation	30.64627946
Sample Mean	1276.222222
Sample Size	9
Confidence Level	90%
Intermediate Calculations
Standard Error of the Mean	10.21542649
Degrees of Freedom	8
t Value	1.8595
Interval Half Width	18.9961
Confidence Interval
Interval Lower Limit	1257.23
Interval Upper Limit	1295.22

a ) sample mean =1276 A.D.

s = 31 yr

b )

lower limit = 1257 A.D.

upper limit=1295 A.D.