Re-calculating thresholds
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- This topic has 1 reply, 2 voices, and was last updated 17 years, 7 months ago by
Bob J.
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December 2, 2004 at 8:17 pm #26225
John ShepherdParticipant@John-ShepherdInclude @John-Shepherd in your post and this person will
be notified via email.Hi – I have a question about re-calcutaing control limits.
Imagine the following :
(1) The process is stable and has been performing within control limits for a long period.
(2) There is some concious change made to the process that alters the performance of that process.
(3) I want to keep the revised process under statistical process control, so presumably I would need to re-set the performance of the new process as soon as I can.
Question is … How can I set the thresholds of my revised process when I have little or no performance data upon which to work ?
Or does this mean that my process goes out of SPC whilst I gather enough data to re-set the limits ?
(expanding the example .. if I collected process stats on a weekly basis, and my original process ran unchanged for 50 weeks, I would be fairly confident of the performance characteristics.
If in week 51 I change the process, how soon can I re-calculate the control limits ?)
Regards John0January 4, 2005 at 7:07 pm #63761Hi John,
You will need to gather 25 subgroups after you revise the process before you can re-calculate the control limits.
Best Regards,
Bob J0 -
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