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Serial mediation model

Posted: Thu Jun 04, 2020 5:16 pm
by lilyv
I have one question about serial mediation model. In my model, Y1 impacts Y2 via 2 mediators (M1 and M2) (cf. Photo). In every papers I read about serial mediation, they always analyze the effect of Y1 on M2 in the model. However, for my model, I don't have any theory base for the relation between Y1 and M2.
So that is my question : In serial mediation model, we have to analyze the effect of Y1 on M2 or this is not necessary ?

I hope that anyone can help me to be cleared about serial mediation model.
Thank in advance.

Re: Serial mediation model

Posted: Tue Jun 23, 2020 11:31 am
by jmbecker
Usually, you also include the paths from Y1 to M2 and M1 to Y2 to show that you actually have a serial mediation and that the mediation is not only through M1 or M2. If you do not specify these additional paths you may find a serial mediation because you have specified an incomplete model. Thus, you want to specify the full model and show that it is actually the Y1->M1->M2->Y2 indirect effect that is significant. For this, you usually also specify a model where you change the sequence of M1 and M2 and show that this would not lead to a serial mediation.