The method of tree ring dating gave the following years A.D. foran archaeological excavation site. Assume that the population ofx values has an approximately normal distribution.
| 1257 | 1320 | 1285 | 1194 | 1268 | 1316 | 1275 | 1317 | 1275 |
(a) Use a calculator with mean and standard deviation keys tofind the sample mean year x and sample standard deviations. (Round your answers to the nearest whole number.)
(b) Find a 90% confidence interval for the mean of all tree ringdates from this archaeological site. (Round your answers to thenearest whole number.)
| lower limit    | A.D. |
| upper limit    | A.D. |
