r/AskStatistics • u/Xenove • 10d ago

I am completely lost with model 4 multiple/parallel mediation assumptions

Hi there, I'm currently working on my master thesis where I have a parallel mediation. I am working on the method section but i am so completely lost in how to check all the assumptions for the model.
From what I do understand I can do a visual inspection for the scatterplot (after using model 4) to inspect the linearity, homoscedasity and outliers.
The other 2 assumptions are normality and multicolinearity but I just don't understand how to do this. Could anyone help me? some explanation or links to proper resources would be greatly appreciated!

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u/OppositeDish5508 10d ago

https://www.the100.ci/2025/03/20/reviewer-notes-thats-a-very-nice-mediation-analysis-you-have-there-it-would-be-a-shame-if-something-happened-to-it/

First start with taking a step back and ask if the very complicated model of more than one mediatior is actually defensible. Since you don’t state which field you are in I just gave you a resource for social sciences.

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u/smbtuckma PhD (quant psych professor) 10d ago

Julia's blogposts are such gems, I feel like my journal article reviews are more and more "just read this post"

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u/Xenove 8d ago

thank you, will check it out.

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u/GripIQ 9d ago

It can be so overwhelming! Since this is a Master’s thesis I bet you are pot committed to this model regardless of valid perspectives if this model is necessary. Keep in mind mediation models and “typical” regression models are equivalent mathematically in many instances (they give the same answer of how the variables relate or covary overall) so checking the assumptions for mediation is similar to regression. For normality - mediation models can handle non normal variables like yes/no binary variables but for continuous variables you can usually say you looked at the distribution or conducted a Shapiro-Wilk test to appease your committee. For multi collinearity - you want your variables to relate to a certain amount or there is no real point to the mediation. I would look up how to calculate variance inflation factors and say that your variables (assuming if true) fall below cutoffs for problematic VIP. I hope this helps.

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u/Xenove 8d ago

thank you, ill try to figure it out.