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From | Richard Williams <richardwilliams.ndu@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: VIF after -ologit- command |
Date | Tue, 08 Mar 2011 17:13:21 -0500 |
At 04:52 PM 3/8/2011, Weichle, Thomas wrote:
Hi Statalisters, It appears as if the VIF command does not work after running an ordered logistic regression model (-ologit- command). In the documentation, I found the following: "In our parameterization, no constant appears, because the effect is absorbed into the cutpoints." Does this help explain why the VIF may not be valid after running the -ologit- command?
We've had variations of this discussion many times on Statalist. Usually (always?) multicollinearity involves the right-hand side of the equation (the Xs) and how you test for it isn't much affected by whether you are using OLS or logit or ologit or whatever. My guess is that -vif- only works after -reg- because other commands don't store the necessary information, not because it isn't valid. You could just "cheat" and run reg followed by vif even if your dv is ordinal. Or, you could download UCLA's -collin- command and use it. For example,
use "http://www.indiana.edu/~jslsoc/stata/spex_data/ordwarm2.dta";, clear ologit warm yr89 male white age ed prst collin yr89 male white age ed prst if e(sample) I didn't need to run the -ologit- command first. I could have also just said use "http://www.indiana.edu/~jslsoc/stata/spex_data/ordwarm2.dta";, clear collin yr89 male white age ed prst if !missing(warm)In other words, when using collin, you just want to make sure that the sample selection is the same as what you would get in your logit or ologit or ols or whatever it is you are doing analysis.
------------------------------------------- Richard Williams, Notre Dame Dept of Sociology OFFICE: (574)631-6668, (574)631-6463 HOME: (574)289-5227 EMAIL: Richard.A.Williams.5@ND.Edu WWW: http://www.nd.edu/~rwilliam * * 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/