Tetrachoric correlation are measures of similarity for dichotomous items,
while polychoric correlation are extensions to the polytomous items. They
are constrained to be between -1 and 1 as the Pearson correlation
coefficients, so it's possible to consider the matrix of these coefficients
as a correlation matrix (between dichotomous or polytomous items).
Jean-Benoit Hardouin
On Sun, 25 Jan 2004 19:59:43 -0000, Nick Cox <[email protected]> wrote:
> I'm in ignorance here.
>
> Are tetrachoric and polychoric just different names for the same kind of
> correlations?
>
> Nick [email protected]
>
--
Jean-Benoit Hardouin
Regional Health Observatory
Orl�ans - France
email : [email protected]
http://anaqol.free.fr
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