A
Andrews
I have heard that SPC manual has changed. Is it true?
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B
Bpoole
It was anounced at the AIAG conference in June that the new SPC manual was going to the printers that week. So the new one should be avaiable soon,
A
Atul Khandekar
Yes. I received this in one of the AIAG newsletters, May '05.
Does anyone know what the changes are? Not much info *** DEAD LINK REMOVED ***.
UPCOMING PRODUCTS
New Edition of SPC To Come: The second edition of the Statistical Process Control (SPC) is planned for release by June. This reference manual describes several statistical methods associated with statistical process control and process capability analysis. The SPC will be available for purchase by calling AIAG customer service at (248) 358-3003.
Does anyone know what the changes are? Not much info *** DEAD LINK REMOVED ***.
B
Bpoole
I Attended the AIAG conference and we were told that the SPC manual was being updated to and include:
> Reduce the details of filling out the forms
> Update the old formats
> Evaluate and improve flow of material
> Improve the quality of the charts and graphics
> Add additional methods and toos
> Expand information on Capability Analysis with non-normal multivariate distributions.
> Make more user friendly
> update the SPC manual to similar layout to other manuals.
> Reduce the details of filling out the forms
> Update the old formats
> Evaluate and improve flow of material
> Improve the quality of the charts and graphics
> Add additional methods and toos
> Expand information on Capability Analysis with non-normal multivariate distributions.
> Make more user friendly
> update the SPC manual to similar layout to other manuals.
M
Mike Smith
SPC Second Edition
I got a email today from the AIAG. The SPC Reference Manual Second Edition is now available for purchase.
I got a email today from the AIAG. The SPC Reference Manual Second Edition is now available for purchase.
A
Andrews
Has anyone gone through the new manual? Have they talked about how non-normal conditions have to be attacked?
Thanks
Andrews
Thanks
Andrews
K
KenK - 2009
Though the content is dramatically reformated, I don't really see anything of much substance changed.
The control chart methodologies are the same. Instead of repeating the control chart process for each type of data, they give an overall methodology and then give the formulas for each type of data. It shortens this section by quite a bit to make room for all the other new stuff.
The capability metrics are essentially unchanged, but has a greatly expanded description of the metrics and their use. One thing new is that this version allows use of s-bar estimation of the variance for Cp & Cpk (the older version only mentioned use of R-bar). There is still no mention of use of pooled variances. The coverage of this topic is much easier to read/understand.
There is a section called "Suggested Use of Process Measures" which says "It is strongly recommended that all four indices (Cp, Cpk and Pp, Ppk) be calculated on the same data set. The comparison of the indices amoung themselves can provide insight to potential process issues and aid in measuring and prioritizing improvement over time." Each metric has its own story to tell -- Ppk is the actual performance, Pp is the "capability" if the process was on center, Cpk is the capability if instability was removed, and Cp is the capaibilty if instability was removed AND the process was on center.
The Second Edition finally cleary states "If the process is in statistical control the process capability will be very close to the process performance. A large difference between the capability and performance estimated sigma indicates the presense of special cause(s)." It is about time.
The non-normal section starts by pointing out the relationship between Cpk, Ppk and the proportion nonconforming (binomial). It then provides two non-normal methodologies, none of which are new: (1) Transformations & (2) Non-Normal Forms (use of statistical distributions other than "Normal").
For transformations they specifically mention Box-Cox and Johnson transformations.
For use of non-normal forms (other distributions) they say to identify the distribution of best fit and then calculate:
Pp = Spec Range / (Q0.99865 - Q0.00135)
where Q0.99 would represent the 99th percentile (Q=quantile; 99% of the population is less Q0.99).
It says that "Cp is calculated as above replacing s with R-bar/d{2}". but I personally don't see where the s is in the Pp formula. I wouldn't have thought Cp was defined when using the percentile (quantile) method.
They do say that there is no analoque of a non-normal Cpk available.
Ppk = min[(USL-xbar)/(Q0.00865-xbar) , (xbar-LSL)/(xbar-Q0.00135)]
The control chart methodologies are the same. Instead of repeating the control chart process for each type of data, they give an overall methodology and then give the formulas for each type of data. It shortens this section by quite a bit to make room for all the other new stuff.
The capability metrics are essentially unchanged, but has a greatly expanded description of the metrics and their use. One thing new is that this version allows use of s-bar estimation of the variance for Cp & Cpk (the older version only mentioned use of R-bar). There is still no mention of use of pooled variances. The coverage of this topic is much easier to read/understand.
There is a section called "Suggested Use of Process Measures" which says "It is strongly recommended that all four indices (Cp, Cpk and Pp, Ppk) be calculated on the same data set. The comparison of the indices amoung themselves can provide insight to potential process issues and aid in measuring and prioritizing improvement over time." Each metric has its own story to tell -- Ppk is the actual performance, Pp is the "capability" if the process was on center, Cpk is the capability if instability was removed, and Cp is the capaibilty if instability was removed AND the process was on center.
The Second Edition finally cleary states "If the process is in statistical control the process capability will be very close to the process performance. A large difference between the capability and performance estimated sigma indicates the presense of special cause(s)." It is about time.
The non-normal section starts by pointing out the relationship between Cpk, Ppk and the proportion nonconforming (binomial). It then provides two non-normal methodologies, none of which are new: (1) Transformations & (2) Non-Normal Forms (use of statistical distributions other than "Normal").
For transformations they specifically mention Box-Cox and Johnson transformations.
For use of non-normal forms (other distributions) they say to identify the distribution of best fit and then calculate:
Pp = Spec Range / (Q0.99865 - Q0.00135)
where Q0.99 would represent the 99th percentile (Q=quantile; 99% of the population is less Q0.99).
It says that "Cp is calculated as above replacing s with R-bar/d{2}". but I personally don't see where the s is in the Pp formula. I wouldn't have thought Cp was defined when using the percentile (quantile) method.
They do say that there is no analoque of a non-normal Cpk available.
Ppk = min[(USL-xbar)/(Q0.00865-xbar) , (xbar-LSL)/(xbar-Q0.00135)]
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