Question: An auditor for the Internal Revenue Service would like to compare the efficiency of four regional tax processing centers. A random sample of five returns was selected at each center, and the number of days between receipt of the tax return and final processing was determined. The results (in days) were as follows:

Regional Center

a) At the .05 level of significance, is there evidence of a difference in the average processing time between the four regional centers? Use an 8-step hypothesis test to answer this question.

b) If appropriate, determine centers are different in average processing time (Use a = .05 and assume that population variances are equal). Note: You are not required to perform an 8-step hypothesis test for each pair; simply identify the critical t and calculated t for each pair and state whether the population mean for each pair is the same or different.

c) What would the auditor conclude? What recommendation might the auditor give to the Internal Revenue Service based on these findings?