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The Braces.jmp data in the Quality Control sample data folder records the defect count in boxes of automobile support braces. A box of braces is one inspection unit. The number of boxes inspected (per day) is the subgroup sample size, which can vary. The u-chart in Figure 4.24 is monitoring the number of brace defects per subgroup sample size. The upper and lower bounds vary according to the number of units inspected.
Note: When you generate a u-chart, and select Capability, JMP launches the Poisson Fit in Distribution and gives a Poisson-specific capability analysis. To use the Capability feature, the unit sizes must be equal.
1.
Select Help > Sample Data Library and open Quality Control/Braces.jmp.
2.
Select Analyze > Quality and Process > Control Chart > U.
3.
Select # defects and click Process.
4.
Select Date and click Sample Label.
5.
Select Unit size and click Unit Size.
6.
Figure 4.24 u-chart

Help created on 3/19/2020