The method of tree-ring dating gave the following years A.D. for an archaeological excavation site. Assume that the population ofxvalues has an approximately normal distribution.

1,2711,3201,1871,3061,2681,3161,2751,3171,275

(a)Use a calculator with mean and standard deviation keys to find the sample mean yearxand sample standard deviations. (Round your answers to the nearest whole number.)

x=___ A.D.

s= ___yr

b)When finding an 90% confidence interval, what is the critical value for confidence level? (Give your answer to three decimal places.)

t_c=__

What is the maximal margin of error when finding a 90% confidence interval for the mean of all tree-ring dates from this archaeological site? (Round your answer to the nearest whole number.)

E=__

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.