RSM CCD Design, which prediction abiliity is best?

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• #37674

Anderson
Participant

Hi all,
Who can advsie which prediction ability is the best among RSM CCD
design CCC, CCI, CCF if without operation limitation and why?
regards,

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#111339

Robert Butler
Participant

I’m not familiar with the designations CCC, CCI, and CCF.  To the best of my knowledge the two major splits for central composite designs are orthogonal and rotatable. If you would let us know what your abbreviations stand for then perhaps I or someone else could give you some assistance.

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#111401

Anderson
Participant

Hi,
You can refer to DOE books by Montogomery, CCD with 3 type,
CCC(with 5 level to detect curvature quadratic effect), CCI(with 5 levels like CCC, but the extreme level didn’t over the original operation interval), CCF (with 3 levels only).  Who can advise?
regards,

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#111423

faceman
Participant

I think that CCC is probably a circumscribed design.
CCI is prbably an inscribed design.
CCF is probably a face centered design.
The CCI and CCC are both five level designs and therefore should give you better prediction equations.
http://www.itl.nist.gov/div898/handbook/pri/section3/pri3361.htm
Regards,
facemen

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#111461

Anderson
Participant

I know the definition of  CCD series, but I saw some paper mentioned the prediction error of CCC,CCI would less than CCF. Yet, considering the extral 2 level (complexity) , overall, CCF is still the first choice?
Can any expert advise me?

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#111475

Robert Butler
Participant

Prediction error is not a function of levels in a design.  It is dependent on the issues of orthogonality and rotatability. CCF designs are not rotatable and they suffer loss of orthogonality with respect to the quadratic terms. Depending on how they are built the CCC and the CCI can either be made to be rotatable and/or orthogonal or not.  You asked
“which prediction ability is the best among RSM CCD
design CCC, CCI, CCF if without operation limitation and why?”
I would interpret you question to mean – If I’m not limited with respect to the number of levels for my factors, which of these designs exhibit the minimum error, with respect to prediction, and minimum change in prediction variance over the region of interest.
If this is an acceptable re-stating of your question then the short answer would be CCC or CCI for the reasons stated above.

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#134507

Didiy
Participant

From what I know, CCC has the best prediction ability. It is rotatable and has the largest design space amongst the three designs. CCI is rotatable, has the smallest design space and has poor prediction ability just like the Box-Behnken design. CCC and CCI require at least 5 number of levels. Both have the same number of runs with any number of factors. I’d suggest using CCC.

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