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Using the telephone numbers listed in your local directory as your population, randomly obtain 20 samples of size. I have attached these numbers in an excel sheet. From each telephone number identified as a source, take the fourth, fifth, and sixth digits.
a. Calculate the mean of the 20 samples
b. Draw a histogram showing the 20 sample means. (Use classes -0.5 to 0.5, 0.5 to 1.5, 1.5 to 2.5 and so on).
c. Describe the distribution of the x-bars that you see in part b (shape of distribution, center, and the amount of dispersion).
d. Draw 20 more samples and add the 20 new x-bars to the histogram in part b. Describe the distribution that seems to be developing.

Use the empirical rule to test for normality. See the sampling distribution of sample means and the central limit theorem develop from your own data!

I need to expand sample size by another 20 phone numbers and then chart the means for all 40 phone numbers. I have added 20 additional phone numbers.
862-9610
862-5482
962-2325
962-2125
962-5562
862-2120
862-2400
862-2522
862-2578
862-5156
962-2128
277-5562
244-6625
244-6632
245-9165
277-5854
222-5546
254-7251
277-6558
214-5574