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.
a. Compute the mean of the 20 samples
b. Draw histogram showing the 20 sample means. (Employ classes -0.5 to 0.5, 0.5 to 1.5, 1.5 to 2.5 and so on).
c. Explain the distribution of the x-bars which 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.