Moderated Mediation

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mvock
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Moderated Mediation

Post by mvock » Fri Dec 10, 2010 2:00 pm

I was wondering whether anyone is familiar with a study using smartPLS to establish moderated mediation?

I am not sure which steps I need to follow to conclude it is moderated mediation, and how to report the outcomes in a paper.
The moderated mediation model I use consists of 3 constructs: the effect of the independent variable (X) on the dependent variable (Y) is mediated by M, and at the same time X moderates the impact of M on Y.

I would be greatful for any suggestions!

jmbecker
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Post by jmbecker » Mon Dec 20, 2010 3:44 pm

HI,
isn't that quite easy? You say that X should moderate M on Y so you have to introduce a product term of XandM (X*M) on Y.

Then, you have a structural model with
X on Y
X on M
M on Y
and
X*M on Y

You can compute X*M with Product-Indicator approach or with the Two-Step approach.

iRose
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Post by iRose » Tue May 03, 2011 12:04 pm

Hi,

I am having the same problem with moderated mediation. Yes, I used the product-indicator approach but I have no idea how to calculate the effect size and predictive relevance of a moderated mediation model.

I've seen that in several published articles, the authors had tested the moderation and mediation effects separately. But is this the correct way given that the piecemeal approach has been criticized by scholars?

I really appreciate answers from anyone who can help me on this. Thanks!

janssengr
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Re: Moderated Mediation

Post by janssengr » Thu Apr 23, 2015 2:39 pm

If I understand this (indeed old ;-)) discussion, this is an example of Model 1 moderated-mediation cf. Preacher Rucker and Hayes 2007.

I can easily specify the interaction term in SmartPLS (on an already existing mediation model):
--> add interaction effect
--> Moderator variable is the 'initial' Independent variable X
--> Independent variable is the 'initial' Mediator variable M
--> Hit Two-stage (or PI as suggested by Dr Becker), and Standardized Product Term generation

But how to assess that mod-med is present?
- if the Interaction Effect is significant (eg 2-tailed T> 1,96, p<0.05), there is moderated-mediation? This is tricky to interpret, as (at least in my case), my Independent variable X is a continuous variable. So how should I interpret this?
- you could do a median-split of the (latent variable score) of Independent variable X, and make data groups of that, for instance Low/High, and use that in a PLS-MGA and assess the bootstrap results. If I'm not mistaken, this is what Preacher et al 2007 suggest. There's also a video on this by James Gaskin (https://www.youtube.com/watch?v=-BI8VweLQPc) that does mod-med using multi-group analysis. In this case, (practical) interpretation is easier, but really impossible with a continous X.
Or am I mistaken?

Choukri
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Re: Moderated Mediation

Post by Choukri » Thu Apr 23, 2015 7:57 pm

Hi,
You should treat to models, Model1: Main effects (X-->M-->Y, at the same model X-->Y), Model 2: Main effect + interaction effects
Good luck

Sakura89
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Re: Moderated Mediation

Post by Sakura89 » Wed Feb 03, 2016 6:21 pm

Dears,

this discussion is even older now. But I have a problem with the same model, namely Model 1 of moderated mediation in Preacher, Rucker & Hayes (2007). Actually, I am not sure about my hypothesis.

My research approach is to investigate how 3 variables are linked to each other. Therefore, I am testing a mediation in hypothesis 1 and a moderation in hypothesis 2. Both is indicated by empirical findings so far.

Those hypotheses result in a model as stated in Model 1: I have an independent variable which might also works as a moderator of the relation between its mediator and the dependent variable.

I just found one (German) study about the investigation of Model 1. The hypothesis there ist that, depending on the IV, the mediator and the DV are either positively or negatively correlated. This seems not to fit to my ideas up to now.

Therefore I would like to know if the hypothesis could also be that, depending on the IV, the effect of the mediator on the DV ist either strong or weak?

I intend to test this hypothesis with the SPPS macro PROCESS later on.

Thank you and all the best!

jmbecker
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Re: Moderated Mediation

Post by jmbecker » Tue Feb 09, 2016 1:46 pm

The basic hypothesis that "depending on the IV, the effect of the mediator on the DV ist either strong or weak?" is ok and can be tested with such a model.
However, if you have a moderated mediation model the system is more complex. You usually do not focus on the hypothesis about direct effects of mediators, but about the indirect effects of your IV through the mediator.
You should think about what your model means for this condition indirect effect (conditional on the IV itself). The hypothesis there seems to be that this indirect effect is itself moderated by the IV (stronger or weaker) depending on the level of the IV.
Self-moderation in turn is something that is closely related to non-linear effects (e.g., quadratic effects), because a simple self-moderation in a direct effect is nothing else that adding a quadratic term.
Dr. Jan-Michael Becker, University of Cologne, SmartPLS Developer
Researchgate: https://www.researchgate.net/profile/Ja ... v=hdr_xprf
GoogleScholar: http://scholar.google.de/citations?user ... AAAJ&hl=de

Sakura89
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Re: Moderated Mediation

Post by Sakura89 » Wed Feb 10, 2016 11:27 am

Thanks a lot!

I got another answer from Kristopher Preacher, who said "Model 1 is relevant in both cases -- when the 'b' part of an indirect effect is theorized to be + or - depending on the IV, and when the 'b' part of an indirect effect is theorized to be strong or weak depending on the IV."

Therefore, I stated the hypothesis as following:

The magnitude of the mediation effect varies depending on the value of the IV.
a) In case the value of the IV is high, the relation of the mediator and the DV is strong.
a) In case the value of the IV is low, the relation of the mediator and the DV is weak.

This isn't exactly what you suggested, right?

Anyway, do you happen to know an article about the preconditions of Model 1? I can't fully apply the work of Massenberg & Kauffeld (2015) about moderated mediation, because of the fact that my IV ist supposed to be the moderator.

More precise, I'm wondering if I still should test this hypothesis with PROCESS, even if I already know that, in a simple moderated regression, the IV turns out not to be a moderator (no signifikant interaction term)? I know that a missing mediation ist not a problem, but what about a missing moderation?

Best, Caro

Man18
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Re: Moderated Mediation

Post by Man18 » Mon May 09, 2016 4:30 pm

Hi every one. I read all the posts here but still confused. I need your help on this please I'm little confused between choosing mediation or moderation or both : i have 2 exogenous variables and 1 dependant & i have 3 hypothesis to test :
h1- x1's impact on y (negative)
h2-x2's impact on y (negative)
h3-x1 increase x2
knowing that in litterature there is an evident interaction between x1 and x2 should i consider x1 as mediator and at the same time consider the moderation also through the interaction between the x1+x2 ?? if this is the case should i put all the arrows (main effect and mediation) in one model or i have to begain by the two first hypothesis test it and then test the model with the 3 hypothesis at the same time.
thank you for any clarification

jmbecker
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Re: Moderated Mediation

Post by jmbecker » Tue Aug 30, 2016 11:29 am

It depends on what precicely is meant by "h3-x1 increase x2"

Do you mean: With increasing x1 the effect of x2 on y is increasing?
Or do you mean: When x1 increases then increases x2 as well?

The first is moderation, the second is mediation.
Dr. Jan-Michael Becker, University of Cologne, SmartPLS Developer
Researchgate: https://www.researchgate.net/profile/Ja ... v=hdr_xprf
GoogleScholar: http://scholar.google.de/citations?user ... AAAJ&hl=de

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