What is the value of Cpk for a new process?

A

austin999

#1
Guys I had a question..

"What is the value of Cpk for a new process?"

I would say nothing. I think for a new process without any data, we cannot calculate Cpk. Am i correct?
Please let me know your views.

thanks in advance.
 
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Jim Wynne

Staff member
Admin
#2
austin999 said:
Guys I had a question..

"What is the value of Cpk for a new process?"

I would say nothing. I think for a new process without any data, we cannot calculate Cpk. Am i correct?
Please let me know your views.

thanks in advance.
Define "new process." If there's no data, there's no basis for calculations. The alternative is to make something up, which is a popular strategy, but not recommended.
 
A

austin999

#3
Thanks for the reply.
Sorry, i had typed my question wrongly.

"What is value of Cpk, when creating a new process?"
 

Jim Wynne

Staff member
Admin
#7
austin999 said:
"What is value of Cpk, when creating a new process?"
rkelly said:
For a new process You should Be looking at PPK and not CPK
austin999 said:
what is Ppk?
rkelly said:
Preliminary process capability
Before this gets out of hand, some clarification is in order. First, it's still not clear what austin999 is asking. Do you want an expected value for a new process? Cpk or Ppk expectations are dictated by the customer. Please tell us more about what you want to know.

Rkelly, there is no generally accepted reason to use Ppk rather than Cpk for new processes. A lot depends on how much data is available, and how it's collected, and Ppk is generally described as a "performance" index, not a "preliminary process capability" index.
 
A

austin999

#8
Hi kelly,

Thanks for your reply.
Can you give more explanation liek how do you calculate Ppk.
And why we cannot calculate Cpk, when creating anew process?
 

Jim Wynne

Staff member
Admin
#9
austin999 said:
Hi kelly,

Thanks for your reply.
Can you give more explanation liek how do you calculate Ppk.
And why we cannot calculate Cpk, when creating anew process?
You can use Cpk if you want to. There's a lot of information on this subject here. Use the search function and you'll find it. Start with the list of links below the posts here on this page.
 
A

austin999

#10
Hi Jim

my question was 'What is the value of Cpk when creating a new process?'
This was the question asked to me..
 
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