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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: RE: PCA and rotation |

Date |
Tue, 22 Dec 2009 11:05:41 -0000 |

Jay's perspective here ("scale development") is that of a psychometrics person. Not all uses of PCA share that objective, or what I understand that term to mean. I.T. Jolliffe. 2002. Principal component analysis. New York: Springer is not quite so negative about rotation of PCs, but does list lots of drawbacks. Nick n.j.cox@durham.ac.uk Verkuilen, Jay Michael I. Lichter wrote: >>What's odd is that I've seen a number of articles that use varimax rotations (with Kaiser normalization) of principal components in scale development. The authors only use the PCA to guide scale development; they perform further analysis with Cronbach's alpha and create summative scales rather than using factor scores. Still, their interpretation of the components are based on rotated component loadings that, at least from Rencher's perspective, are "questionable".<< Rencher is right to be skeptical. Varimax rotation of principal components in the context of scale is nonsense. Nothing in the math of principal components suggests that rotation makes any sense at all (rotation destroys the entire PCA structure's logic!) and similarly nothing in the context of scale development suggests that scales should be orthogonal. If you want a nice article laying this out, look at: K. J. Preacher & R. C. MacCallum. 2003. "Repairing Tom Swift's Electric Factor Analysis Machine." Understanding Statistics, 2, 13-32. This is available at http://kuscholarworks.ku.edu/dspace/handle/1808/1492 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: RE: RE: RE: PCA and rotation***From:*"Verkuilen, Jay" <JVerkuilen@gc.cuny.edu>

**References**:**st: PCA and rotation***From:*"Michael I. Lichter" <mlichter@buffalo.edu>

**st: RE: PCA and rotation***From:*"Verkuilen, Jay" <JVerkuilen@gc.cuny.edu>

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