New to stability studies - What is acceptable?

[robert hollingsbee]

Hi, I'm new to the world of stability studies and i need some help understanding
how to go about performing these. I have read a few books and they still confuse me I have a program that will calculate all of the percentages but i don't know what is considered as being acceptable

ie: 80% ok/not ok what is the specific number related to acceptability. As well choosing your user groups and group size. I have tried a few different methods and have come up with some interesting numbers
ie: 25%/400%/80000% just by manipulating data for these different results. If anyone could help me out i would be a very happy man.
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[Al Dyer]

Robert,

A method that has proven helpful and cost effective:

We use a simple X-R chart to monitor the stability of a gage. As long as you use the same standard (master)and perform the study on a timely basis the Cpk can be monitored over time.

On a weekly basis we measure the standard five times and calculate an ongoing Cpk. This type of graphic presentation works for internal personnel and auditors. Over time we can determine if frequencies are adequate and if masters (standards) and/or gages are wearing.

These records are reported as part of management review fed into a continuous improvement program.

ASD...