Ppk and Pp

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John C. Abnet

Teacher, sensei, kennari
Leader
Super Moderator
#2
If a process has High Pp and Low Ppk? What does that mean?
The "k" refers to the "centering" of the process......(I am NOT a statistician, so someone will jump in and give a more academically accurate answer (I hope ;)

Essentially if Pp is "good" then your process has a minimal amount of variation....i.e. a high potential. However, if the Ppk is "low" then the process is skewed from center. Something that can often be adjusted/corrected.

Hope this helps.

Be well.
 
Last edited:

Bev D

Heretical Statistician
Leader
Super Moderator
#5
We have discussed this several times. See this explanation.
:blowup:Now my obligatory rant: What difference does it make? The whole capability index thing is just statistical alchemy. It is nothing more than an attempt to reduce variation to a single number for lazy people. It destroys knowledge and insight. In the very beginning it had a modicum of usefulness. Then the hacks took hold of it and conflated it with defect rates and tried to add in inferential and distributional statistics which are enumerative at best and have no place in industrial quality. The hacks then said you could understand your process capability and performance with just 30 samples. Too many people keep chasing this evil little number that they have no time left to truly understand their processes and improve quality. :bonk: <rant off>
 

Sebastian

Trusted Information Resource
#6
Many times people confuse SPC with process capability analysis.
I don't care cpk, I care about identification of process variables affecting product attributes.
Then you can prevent/correct quality failures.
 

Jim Wynne

Leader
Admin
#7
We have discussed this several times. See this explanation.
:blowup:Now my obligatory rant: What difference does it make? The whole capability index thing is just statistical alchemy. It is nothing more than an attempt to reduce variation to a single number for lazy people. It destroys knowledge and insight. In the very beginning it had a modicum of usefulness. Then the hacks took hold of it and conflated it with defect rates and tried to add in inferential and distributional statistics which are enumerative at best and have no place in industrial quality. The hacks then said you could understand your process capability and performance with just 30 samples. Too many people keep chasing this evil little number that they have no time left to truly understand their processes and improve quality. :bonk: <rant off>
Yes!!!!
 
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