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Re: st: Testing equality of coefficients in different logistic models
At 11:38 AM 9/13/2006, Sara Mottram wrote:
I would also value opinions on whether there is any value in
performing two binary regressions, given that -gologit2- has an
automatic fitting procedure in -autofit-. (I am basing my analysis
plan on a fairly out of date paper, which suggests that binary
regressions are the only way to choose where non-proportionality is
needed as there were no programs able to do this at the time).
I would suggest downloading and installing Long and Freese's
-spost9-, which includes the -brant- command. This will basically
automate what you propose doing.
My experience is that these different procedures tend to lead you to
the same conclusions, but not always.
Whether or not you use autofit may depend on whether or not you have
any theory as to where the non-proportionalities are. Sometimes
people do, but often they don't. I always say that autofit is
perhaps the lesser of 3 evils. You don't like to use ologit if its
assumptions are violated; but if you switch to mlogit you may be
estimating far more parameters than is necessary. autofit lets you
hit a middle-ground, but you should keep in mind that it relies on
mindless empiricism to get you there!
For more on gologit2, including documentation on its use and some
relatively recent stuff on the rationale behind it, see
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
WWW (personal): http://www.nd.edu/~rwilliam
WWW (department): http://www.nd.edu/~soc
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