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| From | Fernanda Queiros <nandaqueiros@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | st: Categorical mediators and ordinal outcome: using Jackknife to compute the variance of the difference between coefficients |
| Date | Mon, 2 Apr 2012 16:33:02 -0400 |
Dear list participants, First of all, I am a PhD student with limited statistical knowledge compared to what I’ve seen here at the list. Also, English is not my first language; so, forgive me if any part of the message is not crystal clear. I am trying to estimate the mediation effect for an ordinal outcome with 10 levels (ladderw4). The two mediators I’m interested are categorical. My main independent variable (IV) is categorical (four levels), as well as all my co-variates. I am using complex survey data, with 132 PSU’s and 4 strata. I saw here at the list some suggestions applying econometrics methods to a question about testing mediation with categorical mediators, which is beyond my knowledge. Thus, I am trying to compute the difference of my main IV’s coefficients (from the models with and without the mediator) to measure the change and, therefore, mediation effect. I am thinking about using the jackknife procedure to estimate the variance of my coefficients. However, the problem I am facing is that I don’t know how to compute the variance of the difference… That is how I am establishing the survey design using Jackknife (Stata 11.2): . svyset psuscid [pweight=gswgt4_2], strata(region) vce(jackknife) I am, then, using svy: ologit to run my models: (1) without the mediator and (2) with it: (1) xi: svy,subpop(subpop2): ologit ladderw4 i.type_disability age_w4 bio_sex_ i.racew1_r i.parented i.famst3 (2) xi: svy,subpop(subpop2): ologit ladderw4 i.type_disability age_w4 bio_sex_ i.racew1_r i.parented i.famst3 deprew1_dic The output gives me the “final” coefficients and Jackknife SE’s for my IV’s. My question is: - Is there a way to get the coefficients/SE’s for each one of the 132 replications Stata is running in this case? I think that with this information it would be possible to compute the variance of the difference between the two coefficients of my main IV... - Also, does any one have experience on testing mediation with similar types of variables (using complex survey data) and would suggest me a different approach from what I am trying to do? Looking forward to hearing your ideas/suggestions! Many thanks, Fernanda -- Fernanda Queirós Me., Fonoaudióloga / M.S., Brazilian Speech-Language Pathologist Doutoranda - Bolsista CAPES/Fulbright / Ph.D. Candidate - CAPES/Fulbright grantee University of North Carolina at Chapel Hill Gillings School of Global Public Health Department of Maternal and Child Health Para ser grande, sê inteiro: nada teu exagera ou exclui. Sê todo em cada coisa. Põe quanto és no mínimo que fazes.... (Fernando Pessoa) * * 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/