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Re: st: -factor- with binary variables


From   Ronán Conroy <rconroy@rcsi.ie>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: -factor- with binary variables
Date   Mon, 29 Nov 2004 10:49:26 +0000

Patricia Sourdin wrote:

Hi Statalist
just a query on -factor-.
I am trying to construct an index where I have five variables which are binary
indicators.
I have read somewhere that it is not appropriate to use factor analysis if the
variables are binary. Can anyone confirm, please?

Better still, try -msp- and use Mokken scaling. Jean-Benoit Hardouin's site http://anaqol.free.fr is a great resource here. Essentially, if you are building or evaluating a scale it makes more sense to use item response theory to evaluate the scale as a scale. Mokken scaling is a more 'intelligent' approach than just doing KR20s, as it tries to build a coherent scale from your items, and, when it can no longer add items, it tries to use the remainder to build another scale, until the item pool is exhausted.


--

Ronan M Conroy (rconroy@rcsi.ie) Senior Lecturer in Biostatistics Royal College of Surgeons Dublin 2, Ireland +353 1 402 2431 (fax 2764) -------------------- Just say no to drug reps http://www.nofreelunch.org/

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