if Cpk is 0.68, what will be the rejection in ppm?
- June 6, 2007 at 5:30 pm #47190
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For a process we find out the CPk is 0.68. Can we calculate the rejection in ppm from this figure??
what is difference between Ppk and Cpk?
Please help!!0June 6, 2007 at 5:54 pm #157065
Rejection in PPM is somewhere between 20,000 and 40,000 (depends where the process is centered)
Difference between Cpk and Ppk – go read the defintions on this site or go to page 81 of the AIAG SPC manual.0June 6, 2007 at 6:53 pm #157075
The difference between cpk and ppk is simple. Ppk uses sigma while cpk uses sigma hat, or in other words, ppk is your overall process capability while cpk is the capability within your data. Normally these numbers will be very close. However, if you want to create “drama” between the two numbers, take sub-group data. If you have a large discrepency between your subgroups, your cpk and ppk may produce astounding results since cpk uses range to calculate sigma hat. Using Minitab is the easiest and best way to view information and graphical data. Minitab will give you both cpk and ppk and allow you to manipulate data to see0June 6, 2007 at 7:39 pm #157078
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