B
One of my customers told me that one of his customers has shown him a paper which provides sample sizes depending on process capability indices (Pp/Ppk). With this method appropriate sample sizes for process validation could be picked out of a table (without further knowledge about mean, variation, tolerance limits, etc.)
A colleague said that there are "rumors" an interesting paper has been published in which this method is described in detail. (Unfortunately he doesn't know who the author is or where this paper was published and I couldn't find anything in the www).
AFAIK the sample size for Pp/Ppk could be determined based on the accuracy of process capability indices (width of confindence intervals for Pp/Ppk with respect to max. type I error alpha / confidence level 1-alpha), but I haven't seen a method for sample sizes in process validation which takes both error types into account (maximal tolerable risks for type I & type II error / alpha & beta).
Hopefully someone in the Cove could provide further informations about this "sample size based on Pp/Ppk"-method!
Regards,
Barbara
A colleague said that there are "rumors" an interesting paper has been published in which this method is described in detail. (Unfortunately he doesn't know who the author is or where this paper was published and I couldn't find anything in the www).
AFAIK the sample size for Pp/Ppk could be determined based on the accuracy of process capability indices (width of confindence intervals for Pp/Ppk with respect to max. type I error alpha / confidence level 1-alpha), but I haven't seen a method for sample sizes in process validation which takes both error types into account (maximal tolerable risks for type I & type II error / alpha & beta).
Hopefully someone in the Cove could provide further informations about this "sample size based on Pp/Ppk"-method!
Regards,
Barbara
