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. 1,2851,1871,2221,1941,2681,3161,275 1,3171,275

Required:
a. Use a calculator with mean and standard deviation keys to find the sample mean year x and sample standard deviations.
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.)

a) The sample mean is 1260 and the standard deviation is 48.

b) The 90% confidence interval for the mean of all tree-ring dates from this archaeological site is (1230, 1290).

Step-by-step explanation:

Question a:

Mean is the sum of all values divided by the number of values. So

Standard deviation is the square root of the sum of the differences squared between each value and the mean, divided by the one less than the sample size. So

The sample mean is 1260 and the standard deviation is 48.

Question b:

We have the standard deviation for the sample, which means that the t-distribution is used to solve this question.

The first step to solve this problem is finding how many degrees of freedom,which is the sample size subtracted by 1. So

df = 9 - 1 = 8

90% confidence interval

Now, we have to find a value of T, which is found looking at the t table, with 8 degrees of freedom(y-axis) and a confidence level of . So we have T = 1.8595

The margin of error is:

In which s is the standard deviation of the sample and n is the size of the sample.

The lower end of the interval is the sample mean subtracted by M. So it is 1260 - 30 = 1230

The upper end of the interval is the sample mean added to M. So it is 1260 + 30 = 1290

The 90% confidence interval for the mean of all tree-ring dates from this archaeological site is (1230, 1290).

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