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From | "Ariel Linden" <ariel.linden@gmail.com> |
To | <statalist@hsphsun2.harvard.edu> |
Subject | re: st: mediation analysis with proportional data |
Date | Thu, 13 Feb 2014 10:11:37 -0500 |
Hi Sandra, Indeed, linear models for mediation (as well as everything else) are not appropriate for binary Y and X variables. I suggest you consider to different programs: (1) -medeff-, (2) -khb-. Both are user-written programs and can be downloaded from SJ or SSC (findit medeff, findit khb). Additionally, you may want to read the paper referenced below in which we ran simulations under many different X-Y scenarios, and found that both these programs performed very well. I hope this helps Ariel * Linden A, Karlson KB. Using mediation analysis to identify causal mechanisms in disease management interventions. Health Services and Outcomes Research Methodology 2013;13:86-108. Date: Wed, 12 Feb 2014 17:36:56 +0000 From: "Sandra Virgo" <Sandra.Virgo@lshtm.ac.uk> Subject: st: mediation analysis with proportional data Hello all I'd like to know the right type of mediation analysis to use with my proportional data. I am using Stata 13 for Windows. My original regression analysis of these data used a generalised linear model with a logit link i.e. a fractional logit as detailed here: http://www.ats.ucla.edu/stat/stata/faq/proportion.htm The DV is a proportion between 0 and 1, as is the IV and some of the covariates. There are a few actual 0 and 1 values. I now wish to do a mediation analysis with the same data, with the same IV and DV, but testing whether one of the covariates (a proportion between 0 and 1) is a mediator. I also wish to keep the other covariates in. I have read the sem mediation instructions http://www.ats.ucla.edu/stat/stata/faq/sem_mediation.htm but of course I have proportional variables so cannot fit a linear model. Therefore I have used gsem and used a logit link function and binomial family as in the regression analysis. But a colleague has informed me that the output is not valid, and he thinks that there isn't a mediation analysis programme which will suit my data. Should I give up using gsem for these data? If so, is there a better mediation programme for my data? Best Wishes Sandra Virgo PhD student London School of Hygiene & Tropical Medicine * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/