The method of tree ring dating gave the following years AD for an archaeological excavation site. Assume that the population of x values has an approximate normal distribution 1306, 1285, 1215, 1285,...

The method of tree ring dating gave the following years AD for an archaeological excavation site. Assume that the population of x values has an approximate normal distribution    1306, 1285, 1215, 1285, 1268, 1316,1275,1317, and 1275.      A) find the mean and standard deviation b) find a 90% confidence interval for the mean of all tree ring dates from this archaeological site