Using the telephone numbers listed in your local directory
as your population, randomly obtain 20 samples of size 3. From each telephone
number identified as a source, take the fourth, fifth, and sixth digits.
•Calculate the mean of the 20 samples
•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).
•Describe the distribution of the x-bars that you see in
part b (shape of distribution, center, and the amount of dispersion).
•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!