How can you justify forcing factors to be uncorrelated if in fact they are correlated?
Paul
Dr. Paul R. Swank,
Children's Learning Institute
Professor, Department of Pediatrics, Medical School
Adjunct Professor, School of Public Health
University of Texas Health Science Center-Houston
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Rich Ulrich
Sent: Friday, November 18, 2011 9:52 AM
To: [hidden email]
Subject: Re: EFA to CFA( was Re: )
How to better produce a set of items for the next step?
I already suggested the easiest change: Varimax in place of Promax.
Getting rid of some items for their low achieved-communality is a
good idea, cross-loaded or not, since you have too many items
for your N. Then, re-do the factoring. The structure matrix is what
you look at for the loadings.
I've always been worried about getting rid of cross-loaded items.
I know that Varimax will give me theoretically-uncorrelated factors
as defined by proper weights on *every* item on the scale, but the
pragmatic factors will indeed be correlated after I compute them as
averages of the best-loaded items. I always kept an item for its
better-loaded scale when it was .15 or .20 higher on that scale. That
seems like a useful rule for your next step, too.
I sometimes want to keep an item for only the too-short scale when
there are equal loadings for two scales, but that is something that
can be argued in both directions. And it is not unspeakable to keep
one item for both scales. Since your total N is small for the number
of items, you are apt to see quite a few split loadings, even with
Varimax. If you are throwing out more than a few items because of
split loadings - and they aren't ambiguous items when you read them -
you should adjust your rules about what to keep.
This will produce results that are *better*. Whether they are really
pleasing results will depend on whether this sample does own and display
some latent traits that were successfully captured by the test.
--
Rich Ulrich
Date: Fri, 18 Nov 2011 16:57:51 +0800
From: [hidden email]
Subject: EFA to CFA( was Re: )
To: [hidden email]
Dear Rich and all,
Rich said: Poor replication/confirmation could owe to a poor choice of items from the
original set.
Would you able to suggest a method that will produce good items from the original test in order to have good replication/confirmation?
Thank you.
[snip, previous]
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