Create a Statistical Process Control (SPC) Chart In Grapher

What Is an SPC Chart?

Statistical Process Control (SPC) charts use upper and lower control limits to help distinguish between common cause variations and special cause variations. Common cause variations fall within the control limits while special cause variations fall outside the control limits. SPC charts are a powerful asset for meeting high-quality standards and improving processes.

How to Create an SPC Chart In Grapher

You can create Statistical Process Control (SPC) charts in which the graph contains upper and lower control limits for your data. SPC charts use function plots to define the upper and lower control limits, the mean line, as well as any other desired limits. Follow these steps to create an SPC chart in Grapher.

1. Click Home | New Graph | Line/Scatter and select Line Plot. 
2. In the Open Worksheet dialog, navigate to the data file and click Open. 
3. In the Object Manager, click on the Graph to select it. 
4. Click Graph Tools | Add to Graph | Plot and select Function Plot - Y = F(X)
5. In the Choose Axes dialog, select the graph and axes you would like to add the function plot to. Click OK.
6. In the Object Manager, click on the Function Plot to select it.
7. In the Property Manager, click the Plot tab
8. In the Plot Options section, set Y = F(X) to the value of your upper control limit (UCL).
   
9. Repeat steps 3-8 for your lower control limit, mean line, and any other desired limits. You can also use the Duplicate command by right-clicking on the Function Plot in the Object Manager or using Home | Clipboard | Duplicate for greater efficiency.
   
10. Using the Object Manager and Property Manager, you can customize your Line Plot, Function Plots, and Axes to your liking.