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From |
"YP Choi" <choiyp@cuhk.edu.hk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: How to obtain intercepts using svyologit |

Date |
Tue, 22 Feb 2005 14:16:39 +0800 |

Dear Richard, Thanks for your clarification. It is very helpful. Regards Susanne -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Richard Williams Sent: Tuesday, February 22, 2005 8:39 AM To: statalist@hsphsun2.harvard.edu Subject: Re: st: How to obtain intercepts using svyologit At 03:05 PM 2/21/2005 +0800, YP Choi wrote: >Dear all, > >I am using the survey commands in stata to analyze stratified data. I >am running some ordinal logistic regressing models and want to know how >I can obtain the odds ratio of the intercepts? Many thanks for your >help. Somebody can correct me if I am wrong, but I don't believe the term "odds ratio" is appropriate when referring to the intercept (which is why Stata doesn't report it in the column labeled odds ratio; although other programs like SPSS will have a column labeled EXP(B) which includes the intercept). The idea of the odds ratio is that you are contrasting the odds of 2 otherwise identical cases where one case scores 1 unit higher on the X variable in question. For a constant, this doesn't make any sense, since all cases have a score of one on the constant. Nonetheless, in some contexts, you might be interested in the exponentiated intercept, e.g. in a logistic regression, an intercept of zero would tell you that somebody who scored 0 on all the Xs would have exp(0) = 1 odds of success, which corresponds to a 50% chance of success. If the intercept was 1, the probability of success for somebody scoring 0 on all the Xs would be 73.1%. If there are no Xs in the model, e.g. you just do -logit y- , then the exponentiated intercept gives you the overall odds of success. In ordinal logistic regression, however, Stata reports cutpoints, not intercepts. Again, maybe somebody can enlighten me here, but I am not sure what an exponentiated cutpoint would mean, at least when there is more than 1 cutpoint. (If there is only 1 cutpoint, it has the same value but opposite sign of what you get when you run a logistic regression.) But, if you really want exponentiated intercepts or cutpoints, there is always your calculator, or the -display- command in Stata. ------------------------------------------- Richard Williams, Notre Dame Dept of Sociology OFFICE: (574)631-6668, (574)631-6463 FAX: (574)288-4373 HOME: (574)289-5227 EMAIL: Richard.A.Williams.5@ND.Edu WWW (personal): http://www.nd.edu/~rwilliam WWW (department): http://www.nd.edu/~soc * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: How to obtain intercepts using svyologit***From:*Richard Williams <Richard.A.Williams.5@nd.edu>

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