A control chart is a graphical and analytic tool for monitoring process variation. We can use Control Chart Builder to create control charts of your process data.
Here, I have the Socket Thickness sample data table, which includes measurements for the thickness of sockets. There has been an increase in the number of defects during production, and we need to investigate why this is occurring.
I'll use Control Chart Builder to investigate the variability in the data and the control of the process.
First I need the data, from Help then Sample Data Library then Quality Control open Socket Thickness.jmp.
Select Analyze then Quality and Process then Control Chart Builder.
Drag Thickness to the Y zone.
Drag Hour to the Subgroup zone...at the bottom.
Looking at the Average chart, you can see that there are several points below the lower control limit of 7.788772.
I want to start investigating if another variable might be contributing to the problem.
So I'll drag Cavity into the Phase zone.
From the Average chart, I can now conclude:
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.
Try this in JMP for yourself by selecting Analyze then Quality and Process then Control Chart Builder.