Several moderation effects - How to analyze?

[Jeremias]

Hi,

I got a question regarding two moderation effects in one model. As far as I know, it´s important to analyze first the model without any moderation effects.

Than add the moderation effects and analyze them.

But I have 2 of them in my model.

So should I insert Moderation effect 1, analyze the model and delet Mod-Effect 1 bevor I add the second one? Thus evaluate the results separatly.

Or insert both of them parallel and evaluate them at the same time?

I hope anyone can help me, cause I can´t find anything in the literature.

Thanks

Jeremias

[jmbecker]

The correct approach would be to analyze all moderators together. Many people also find it useful to show robustness of the results analyzing each moderator separately before combining both in one model. From analyzing both separately you can also learn about potential problems that may arise when combining both moderators.

Concerning the comparison of model with and without moderators you need to take into account that you have a different interpretation of effects: main effects / unconditional effects in the model without moderator vs. simple / conditional effects with moderator(s).