Stefan Duke wrote:
I have question concerning factor analysis on variables with different
measurement levels.
The questionnaire consists of binary and ordinal variables. If I would
have just binary variables, I would use the tetrachoric correlation
coefficients. For the ordinal I assume approx. normality and then use
the ordinary factor analysis capability.
But what do I do when I have both variables? Is it an option to
construct the variance-covariance matrix by hand? And what do I take
for the correlation between binary and ordinal?
Maybe is there a model class which takes care of that, that yields
similar outcomes as factor analysis but can deal with such kind of
data (e.g. correspondence analysis).
--------------------------------------------------------------------------------
You can use -polychoric-, a user-written command available from SSC that handles
datasets like yours. There's a chance that the matrix will not be at least
positive semidefinite, but you can use the -forcepsd- option of -factormat- for
that.
Joseph Coveney
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