Visual Six Sigma: Making Data Analysis Lean

8.3. Reviewing Historical Data

Carl and his team are now ready to start thinking about data. They decide that a good starting point is to review the prior crisis team's data and analysis.

8.3.1. Data from Prior Crisis Team

To their surprise and delight, the team members find that the prior crisis team had used many Six Sigma tools in investigating possible causes of the problem. In particular, the team members had developed an Input/Output process map (Exhibit 8.13) to help identify the potential Xs that might be driving variation in MFI, CI, and, consequently, Yield. They used the Xs and Ys identified in their process map to determine the data they should collect.

Figure 8.13. Input/Output Process Map of White Polymer Process

Carl obtains a spreadsheet of the data collected by the crisis team and imports this into a JMP table, which he calls CrisisTeamData.jmp. The data consist of measurements for the Xs and Ys identified in the process map for 127 batches over about a six-week period. A partial view of the data file is shown in Exhibit 8.14.

Figure 8.14. Partial View of Table Containing Crisis Team Data

The columns in the data table are described in Exhibit 8.15. Note that there are three Ys and eight Xs of interest. Carl realizes that even though the table does not have ...