An accounting firm that specializes in auditing the financial records of large corporations is interested in evaluating the appropriateness of the fees it charges for its services. As part of its evaluation, it wants to compare the costs it incurs in auditing corporations of different sizes. The accounting firm decided to measure the size of its client corporations in terms of their yearly sales.Accordingly, its population of client corporations was divided into three subpopulations:

A: Those with sales over $250 million B: Those with sales between $100 million and

$250 million C: Those with sales under $100 million The firm chose random samples of 10 corporations from cach of the subpopulations and determined the costs (in thousands of dollars), given in the accompanying table, from its records.

a. ~&struct a dot plot for the sample data, using different types of dots for each of the three samples. Indicate the location of each of the sample means. Based on the information reflected in your dot plot, do you believe that a significant difference exists among the subpopulation means? Explain.

b. SAS was used to conduct the analysis of variance calculations, resulting in the printout shown below.

Conduct a test to determine whether the three classes of firms have different mean costs incurred in audits. Use a = .05.

c. What is the observed significance level for the test in part b? Interpret it.

d. What assumptions must be met in order to ensure the validity of the inferences you made in parts b and c?