st: Interpreting mediation model sobel goodman test

["Meredith T. Niles" <mtniles@ucdavis.edu>]

Hello all,
  I am working on running multiple and single mediation models to assess
farmer climate change perceptions and potential adoption of climate
change practices.  I am getting an odd result when running a Sobel
goodman test in Stata with regards to the portion of total effect that
is mediated (5.139).  Does anyone have any perspective on why this
number is so large?  Running the same test with another set of climate
change practices yields a proportion of total effect that is mediated at
0.79 which seems much more in line with other results I've seen. 


Sobel-Goodman Mediation Tests

             Coef         Std Err     Z           P>|Z|
Sobel       -.09959383    .05075882  -1.962      .04975096
Goodman-1   -.09959383    .05217108  -1.909      .05626401
Goodman-2   -.09959383    .04930612   -2.02      .04339293

Indirect effect = -.09959383
  Direct effect = .08021537
   Total effect = -.01937846

Proportion of total effect that is mediated:  5.1394091
Ratio of indirect to direct effect:      -1.2415804 


Thanks for your thoughts.

Best,
Meredith Niles


PhD Candidate, Graduate Group in Ecology
NSF REACH IGERT Trainee
Deputy External Chair, Graduate Student Association
University of California, Davis
2126 Wickson
http://environmentalpolicy.ucdavis.edu


*
*   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/