National Products is a distributor of printer and copier paper for commercial use. The data file called Sales contains the annual, year-to-date sales values for each of the company’s customers. Suppose the internal audit department has decided to audit a sample of these accounts. Specifically, they have decided to sample 36 accounts. However, before they actually conduct the in-depth audit (a process that involves tracking all transactions for each sampled account), they want to be sure that the sample they have selected is representative of the population.

a. Compute the population mean.

b. Use all the data in the population to develop a frequency distribution and histogram.

c. Calculate the proportion of accounts for customers in each region of the country.

d. Select a random sample of accounts. Develop a frequency distribution for these sample data.

Compare this distribution to that of the population.

(Hint: You might want to consider using relative frequencies for comparison purposes.)

e. Construct a 95% confidence interval estimate for the population mean sales per customer.

Discuss how you would use this interval estimate to help determine whether the sample is a good representation of the population. (Hint: You may want to use the finite population correction factor, since the sample is large relative to the size of the population.)

f. Use the information developed in parts a through e to draw a conclusion about whether the sample is a representative sample of the population. What other information would be desirable? Discuss.