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st: Theoretical/manual rotation of factors?


From   George Stimson <stimson@netz.us>
To   statalist@hsphsun2.harvard.edu
Subject   st: Theoretical/manual rotation of factors?
Date   Tue, 20 Jun 2006 23:38:30 GMT

I would appreciate advice or information 
on whether it is possible to perform a 
subjective/manual rotation for 
theoretical purposes when conducting 
factor analysis with Stata 9.2.  I'll 
try to explain my purpose with a 
hypothetical example.

Assume I have a correlation matrix of 10 
attitudinal items and that in previous 
research Item 1 has been identified as 
highly representative (an ideal type) of 
a certain theoretical trait and that 
Item 10 has been identified as highly 
representative (a different ideal type) 
of a different (but not 
necessarily orthogonal) theoretical 
trait.  If I were to factor analyze the 
correlation matrix and observe the 
factors on which each of these two items 
loads highest after some traditional 
orthogonal or oblique rotation, I would 
expect that Item 1 would have a 
significant and higher (or bi-polar, 
negative) loading than Item 10 on one 
factor and that the reverse would hold 
for the relationship of the two items on 
a second factor.  It is possible, 
however, given sampling and other 
issues, that neither Item 1 nor Item 10 
would actually be the highest loaded 
items on their respective factors in my 
sample after traditional factor rotation 
strategies designed to achieve simple 
structure.  I would like, therefore, to 
manually rotate the factors to achieve 
this objective of maximizing the 
loadings of Items 1 and 10 on their 
respective factors to the extent 
possible. 

That is, I would like, for theory 
testing purposes, to be able to rotate 
the factors manually so that I can find 
a factor solution in which the loadings 
of Item 1 and Item 10 are maximized as 
much as possible on their respective 
factors.  Is such a rotation strategy 
available in Stata?

Thanks for any information or advice.

George
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