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From |
"Nick Cox" <[email protected]> |

To |
<[email protected]> |

Subject |
st: RE: RE: Factor Analysis with ordinal and binary variables |

Date |
Tue, 2 Jun 2009 16:32:28 +0100 |

Joseph's answer may be what you are looking for, but here as often I am puzzled by the tacit assumption that there is always a technical fix for a technical question regardless of the problem-situation and what the researcher is trying to do. Instead of asking "what do I do?" why not ask yourself whether feeding a mix of variables to a factor analysis is a reasonable thing to do given your scientific or practical objectives. As you don't state the latter, it is difficult even for those people who may have similar objectives or experiences to comment. Otherwise put, Stata doesn't in any sense know that your variables are on different measurement levels; that's largely in the researcher's head. Similarly, Stata doesn't know that you are "assuming" approximate normality. Nick [email protected] Joseph Coveney 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. 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). * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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