Recently, I performed a study in which I needed to test for dual mediation – when the
indirect effect of Y on X goes through two mediators
(pictured here).  Whenever I need to test for mediation or moderation of any type, I first go to Hayes’s PROCESS macro for SPSS.  It is easy, and it adheres to most all
current best-practices.  If you don’t have it yet, I STRONGLY suggest that you download it now:  http://www.processmacro.org/index.html .  It has saved me hours (days?) on statistical analyses.

So, I opened up the documentation for PROCESS and I found…that it does not have a model for dual mediation!  Of all things, I would have assumed that PROCESS would be able to test for dual mediation!

I searched online for solutions, and I even referred to mediation textbooks to
devise a formula to test for dual mediation.  After having moderate success, I
finally went back to PROCESS.  Out of frustration, I set the program to test the traditional mediation model (with one mediator), but I included two mediators in the dialogue window.  And what did I see?  It provided output for dual mediation!

While this information may not be groundbreaking, it certainly helped me.  I hope that it can also help someone who is as frustrated with dual mediation as I was.  The permanent page for dual mediation testing can be found here:  Testing for Dual Mediation .

If you need any help running dual mediation in process (or any other statistical questions), feel free to email me at MHoward@SouthAlabama.edu.  I always
enjoy hearing from people running interesting statistics!