Visual Six Sigma: Making Data Analysis Lean

7.5. A Deeper Understanding of Regional Differences

Rick's next charge is to determine whether there are regional differences in performance relative to sales of Pharma Inc.'s major product. He realizes that he has already gone a long way toward answering this question. Yes, there are statistical differences between the regions, as indicated by the Compare Means analysis illustrated in Exhibit 7.39 and reinforced by the model that accounts for the sales representative effect (Exhibit 7.44). Rick can say that in terms of total prescriptions written over the eight-month period the regions fall into six groups, as shown in Exhibit 7.42. The important questions now revolve around the practical extent of such differences and which chunk factors are related to the differences.

So at this point, Rick wants to go beyond the counts of written prescriptions. Again, he has already done some of the work to understand the relationship between the number of prescriptions and the number of visits. Now he wants to see if he can gain additional insight by seeing this from the perspective of the sales representatives and by taking into account behavior over time. In fact, when Rick thinks about this, he realizes that he would like to see, on a year-to-date basis, how the total number of prescriptions written by each sales representative's physicians is related to the total number of visits. But he would also like to be able to visualize the effect of the total number of physicians assigned to a ...