Managers are commonly fed a diet of report-card data. These data have usually been aggregated into summaries, averages, and totals to characterize the big picture. As useful as such summaries can be, they can also be an obstacle to an effective analysis. Here, we’ll learn how to avoid this obstacle.

Our example will come from a plant producing steering wheels. At the end of the production line, the inspectors would either pack the wheels for shipment to the assembly plant or place them on a line going to the rework department. Each day, Andy would visit the inspection station to conduct a 60-piece audit. When one of the inspectors rejected a wheel, she would tell Andy why she had rejected that wheel. Andy would add a tick mark to his sheet, and after 60 wheels had passed he would return to the quality office across the street and record the data.

The chart Andy produced for management consumption was an np-chart showing the total number of wheels rejected for each audit. This report-card chart is shown in Figure 1.

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