Hi All,

In one of the website recently I read that Cp and Cpk consider the deviation mean within rational subgroups, while Pp and Ppk set the deviation based on studied data.

Here I would like to know about, what is difference between rational subgroups and studied data?

And what are the major differences between Cp, Cpk and Pp, Ppk?

Thanks & Regards

Durga

The difference in Cp and Pp lies in the way standard deviation is calculated. Same difference lies between Cpk and Ppk. 

Pp (and Ppk) considers OVERALL Variation while Cp (and Cpk) considers WITHIN GROUP Variation. Or in other words, Pp ignores grouping of any kind. 

If you have completed your Black Belt, please have a close look at the formula. 

Best Regards, 

VK

 

Thanks Vk,

I haven't done my black belt, but I am looking for it.

Thanks & Regards

Durga