🚀 go-pugleaf

In article <1992Nov3.113547.3959@memstvx1.memst.edu>, rajagopa@memstvx1.memst.edu writes:
|> Dear friends,
|> 	      Could some of you stat buffs let me know the concept of
|> factor analysis and rotation in plain english. I do not quite get the hang 
|> of it. I thank your responses and will post the compiled version on the net.
|> Thanks/Raj
|> 

There are several ways of approaching the rotation issue.  One is to
view it historically from a "simple structure" standpoint. In this
case, a decent text to read is Thurstone's "Multiple Factor Analysis".
What he says is that simple structure rotation attempts to find a
linear transformation ("rotation") which results in repositioning the
initial (unrotated) factors in hyperspace such that the variable
configuration is simplified as much as possible.  He lists 5 rules to
help the graphical rotators of the 1940's achieve this by using the
concept of a hyperplane.  In doing simple structure rotation, one
typically isolates subsets of highly interrelated variables which
covary similarly.  There is some overlap with the concepts of cluster
analysis.  With the advent of computers, hand rotation has become
nearly a lost art and most analysts depend upon some algebraic
expression which attempts to fulfill some of Thursone's concepts (ie,
Varimax).

Another way of looking at factor rotation is from a quasi-confirmatory
view.  In such a situation, one might wish to look for a predetermined
factor loading structure by finding a least-squares fit between a low
dimensional subset of factors and some preconceived loadings.  This
type of rotation is known as target rotation.  The most straightforward
description of the concepts behind rotation is probably Rummel's (1970)
text, Applied Factor Analysis, Northwestern U. Press.  I also have a
review article on rotation of principal components, which includes a
Monte Carlo test of the accuracy of available algorithms, should that
interest you.
---
Mike Richman                        !CIMMS/The University of Oklahoma
richman@reepicheep.gcn.uoknor.edu   !100 East Boyd, Room 1110
405-325-3460 (office) 325-7614 (fax)!Norman, OK  73019-0628  USA