st: mediation analysis with proportional data

["Sandra Virgo" <Sandra.Virgo@lshtm.ac.uk>]

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


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