Attribute Control Charts – C and U Charts

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This guide provides instructions on creating C and U attribute control charts. C charts are often used to plot the number of nonconformities (or defects) in a subgroup that usually, but not necessarily, consists of one inspection unit, while U charts are often used to plot the number of nonconformities per unit, where the number of units per subgroup can vary.   

 C Charts

1. From an open JMP^® data table, select Analyze > Quality and Process > Control Chart > C Control Chart.
2. Select one or more continuous variables from Select Columns, and click Process.   
3. Select the column defining the unit size (if not a constant size) and place in the n Trials role. Click OK.
   Note: If sample sizes are not constant, the control limits will vary.   
   
   

U Charts (or DPU Charts)

1. From an open JMP data table, select Analyze > Quality and Process > Control Chart > U Control Chart.
2. Select one or more continuous variables from Select Columns, and click Process.   
3. Select the column defining the unit size (if not a constant size) and place in the n Trials role. Click OK. 

In the example below, the number of defects (# defects) per unit inspected (Unit Size) is plotted on a U Note: Since the Unit size is not constant, the control limits vary.

Tips:

• The process variable must be sorted in time order.
• Many options, such as tests for special causes and capability analysis, are available from the red triangles.

Fabric.jmp (Help > Sample Data Folder > Quality Control)

Example: Braces.jmp (Help > Sample Data > Quality Control)

Visit Quality and Process Methods > Legacy Control Charts in JMP Help to learn more.