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RE: st: PCA and rotation

From   "Verkuilen, Jay" <[email protected]>
To   "'[email protected]'" <[email protected]>
Subject   RE: st: PCA and rotation
Date   Mon, 4 Jan 2010 15:33:21 -0500

Nick Cox wrote:

>These recommendations sound tendentious to me, except that no doubt they make much sense in the context of the authors' aims. The idea that factor analysis is _uniformly_ superior to principal component analysis is I think only defensible if your aims are limited to those addressed explicitly by factor analysis. <

I would agree. There are reasons to use PCA and reasons to use factor analysis. Despite superficial similarities, they're not the same procedures. 

>Indeed, even non-experts on intelligence tests can guess that different intelligence factors, if they exist, are most unlikely >to be uncorrelated, 

Too bad far too many psychologists grew up on "Little Jiffy".... 

but there are plenty of contexts (e.g. in meteorology and oceanography) in which orthogonal components are >precisely what is desired from a physical point of view. 

Orthogonality is a separate question, though. You can have orthogonal factor analysis. Orthogonality can also be something subject to statistical test, e.g., by showing that certain factor correlations == 0. 


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