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This thread is carried over and continued in the Current Elsmar Cove Forums 
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This thread is carried over and continued in the Current Elsmar Cove Forums
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The New Elsmar Cove Forums
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 The New Elsmar Cove ForumsThe Elsmar Cove Forums
 Statistical Techniques and 6 Sigma
 precontrol and process capability
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| Author | Topic: precontrol and process capability |
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dmac Lurker (<10 Posts) Posts: 1 |
posted 26 July 2001 02:10 PM
   
Are there any statistical formulas that relate precontrol data to process capability indices? IP: Logged |
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D.Scott Forum Contributor Posts: 53 |
posted 26 July 2001 02:55 PM
dmac - I am not sure this is what you are looking for but here it is anyway for what it is worth. To establish a pre-control chart, it must be assumed that the process is normally distributed with a Cpk of at least 1.0. It can then be statistically shown that 86% of the product will be within the control lines with 7% in each of the other sections. As there is no statistical data taken or analyzed, it is important to only use pre-control on a process known to be stable. I am sure there are others who can add a lot to this but at least it may help to get you started. Dave IP: Logged |
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MSAFAI Forum Contributor Posts: 42 |
posted 30 July 2001 12:53 PM
1- Check normality by using a Histogram of your data. 2- You can have a ROUGH estimate of process capability by taking standard deviation of your data and calculating Ppk. 3- I don't know to what extent you can rely on the above calculation, because using a Pre-control chart you cannot be sure your process is under control (a prerequisit to determining capability) Any other ideas? MSAFAI IP: Logged |
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