Descriptive statistics
Statistical tests
Design of Experiment
Gage RR
Problem resolution
Reliability
Control plan
Menu della guida per l'utente

Guida utente

Centering the Ppk procedure

Calculations of the Cp and Pp do not take into account the process variability or procedure centering. Indeed, the following figure shows that the two processes have a Pp of 1.6.
Ppk illustration 2
Ppk illustration 3
It is clear that the lower process creates more off-tolerance parts than the left hand process. Yet, this is not seen in the pp calculation because, for the two processes, we have:
It is therefore appropriate to introduce a new indicator, the Ppk. The Ppk corresponds to the true procedure performance and is calculated in the following way:
Let us take the following example:
Ppk illustration 2
In this case:

Let us take the following example:

Ppk illustration 3
In this case:
The Ppk makes it possible to differentiate the two processes.
In the same way, the Cpk can be calculated, which is the equivalent of the Ppk but uses short term variability.

Una soluzione completa per l'Industria 4.0

8 moduli statistici

trial

Test

0

30 giorni

Testalo gratuitamente

APC

SPC

Controllo

Analisi

check

30 giorni

check

Tutte le funzioni di Ellistat

check

1 utente

Supporto tecnico e ed aggiornamenti inclusi

student

Studente / Insegnante

0

1 anno

Checkout

Analisi

check

1 anno

check

Tutte le funzioni di Ellistat

check

1 utente

check

Licenza dedicata agli studenti che dispongono di una tessera studente in corso di validità

Supporto tecnico e ed aggiornamenti inclusi

standard

Standard

49

per utente al mese

Checkout

Analisi

check

Licenza rinnovata ogni mese

check

Tutte le funzioni di Ellistat

check

Utenti illimitati

check

Supporto tecnico e ed aggiornamenti inclusi