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Drew
Level I

Cpm Calculation issue within XBar Chart

I have been trying to recreate the JMP calculations in SQL and can duplicate all of the process controls with the exception of Cpm.  I am using JMP 12 and the Cpm formula from the "Process Capability in JMP 12 - A New Look" article.  The equation is also on the image of the Xbar chart.  I have include a .jmp data file to recreate the chart to see if the calculated Cpm is what you expect.  Any help would be appreciated.  Here are the calculated values using SQL:

Cp

Cpk

Cpm

Cpl

Cpu

Sigma

Average

6.945

4.855

6.944

9.036

4.855

0.04799

0.301

 

XbarChart.png

1 ACCEPTED SOLUTION

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Re: Cpm Calculation issue within XBar Chart

The formula given in the version 12 documentation was incorrect.  This was corrected in the version 13 documentation.

View solution in original post

2 REPLIES 2
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Re: Cpm Calculation issue within XBar Chart

LSL=-1;
Target=.3;
USL=1;
Mean=0.300960716247559;
Sigma=0.0479930638148251;
cpm=min(Target-LSL, USL-Target)/(3*sqrt(Sigma*Sigma+(Mean-Target)^2));

Mean and Sigma can be found by running the distribution platform on the response variable.

Highlighted

Re: Cpm Calculation issue within XBar Chart

The formula given in the version 12 documentation was incorrect.  This was corrected in the version 13 documentation.

View solution in original post

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