Example of the Control Chart Builder

This example uses the Socket Thickness.jmp sample data table, which includes measurements for the thickness of sockets. There has been an increase in the number of defects during production and you want to investigate why this is occurring. Use Control Chart Builder to investigate the variability in the data and the control of the process.

Select Help > Sample Data Library and open Quality Control/Socket Thickness.jmp.

Select Analyze > Quality and Process > Control Chart Builder.

Drag Thickness to the Y zone.

Drag Hour to the Subgroup zone (at bottom).

Figure 2.2 Control Charts for Socket Thickness

Looking at the Average chart, you can see that there are several points below the lower control limit of 7.788772. You want to see whether another variable might be contributing to the problem.

Drag Cavity into the Phase zone.

Figure 2.3 Control Charts for Each Cavity

From the Average chart, you can conclude the following:

•

There are differences between the cavities, each deserving separate control limits.

•

Cavity 1 is producing sockets with a higher average thickness, indicating that further investigation of the differences between cavities is warranted.

•

All of the cavities have points that are outside the control limits. Therefore, you should investigate the lack of control in the data for each cavity.

The Range chart for each cavity shows that the within-subgroup measurements are in control.