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Matthaneeya
Level I

CPK CPU CP is equal to zero, what can happen from?

 
6 REPLIES 6
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txnelson
Super User

Re: CPK CPU CP is equal to zero, what can happen from?

funny data, bad limits, bug in JMP, it is the correct results???????? You need to provide more specific information. Sample data would really help.
Jim
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Matthaneeya
Level I

Re: CPK CPU CP is equal to zero, what can happen from?

Please see my data as below

 

No.Length (mm)
1302
2300
3300
4305
5303
6305
7302
8303
9305
10304
11305
12305
13305
14304
15305
16304
17302
18303
19304
20303
21303
22304
23302
24303
*Specification295 - 325
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txnelson
Super User

Re: CPK CPU CP is equal to zero, what can happen from?

I apparently are not understanding your question.  Here are my results of Cp and Cpk for your data

capability.PNG

Jim
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Matthaneeya
Level I

Re: CPK CPU CP is equal to zero, what can happen from?

Hi txnelson,

    Thank you for the reccommendation but normally I use Cpk from "Quantile sigma" , it is shown like below.

     Can I ask more question, between Cpk from  "Long term sigma" and "Quantile sigma" , in which case should we use it?

Thank you

 

CpK.jpg

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David_Burnham
Super User

Re: CPK CPU CP is equal to zero, what can happen from?

Oh and by the way you are using a SHASH distribution!

-Dave
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David_Burnham
Super User

Re: CPK CPU CP is equal to zero, what can happen from?

I'm not sure why the SHASH distribution gives zero as the result but I've not had much success using SHASH for process capability.  In your case your data only has 5 distinct levels, and the distribution requires 5 parameter estimates so you really are running out of degrees of freedom and the SHASH is probably a total over-fit of your data.

-Dave
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