Capability analysis
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newbie.
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September 25, 2008 at 9:02 am #51005
Hello,
Does anyone have instructions on how to perform a capability analysis for both normal and non-normal data?
cheers0September 25, 2008 at 10:43 am #176122
statfinderMember@statfinderInclude @statfinder in your post and this person will
be notified via email.Hi
Capability for Normal data can be calculated by
CpK = Min ((USL-average)/3 stdev or (Average – LSL)/3 stdev)
or Z = (Target – Average)/3 stdev
If it is Non-Normal either try to transform your data using Johnson or Box-cox transformation.
0September 25, 2008 at 10:59 am #176124Hello,
Thanks for this, however I would also like to know the overall approach for doing a capability trial in terms of assessing whether a new piece of equipment was suitable to use for the manufacture of product. Does anyone have instructions on how to go about this?
0September 25, 2008 at 11:42 am #176126Forget the transform crap – it’s bad advice.
0September 29, 2008 at 5:58 am #176216
statfinderMember@statfinderInclude @statfinder in your post and this person will
be notified via email.The capability analysis for new equipment can be calculated using Machine capability analysis. Take continuous 50 samples without interruption and calculate CpM with stdev calculation alone changes in Cpk formula
Sigma = Sqrt((individual value – set value)^2/ n-1)
0September 29, 2008 at 9:55 am #176223Thanks for your help.
0September 29, 2008 at 1:48 pm #176231Hi Stan,
I know that transformation for the purpose of studying capability isnt necessary, but is it harmful to an analysis?
And I can’t help feeling as if capability indices themselves are somewhat bogus. When I read about all the assumptions and variability that go into the various models, would not using a standardized procedure on actual process performance to capture yield / confidence intervals be easier to apply, explain, and manage to?
Am I off base here?
Thank you.0 -
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