Quadratic effect

[AR79]

Hello,

The model has two moderators (please see the attached).
An error is displayed while assessing the quadratic effects, saying, 'The combination of different interaction effects is not possible'.

Does this mean that in assessing the robustness using quadratic effects, I need to consider only the main model, leaving aside the moderators? Alternatively, what can be done to address this error?

Kind regards,
AR79

Quadratic effects with moderators.jpg (112.72 KiB) Viewed 76 times

[jmbecker]

We have, for now, disabled the inclusion of both quadratic and interactions terms because it is not directly clear what the correct model would be. There is also little guidance in the literature about such types of models.

When you have an interaction, you have a conditional effect: The effect of X on Y depends on the moderator M.

Are you assuming that the conditional effect is quadratic? Are you assuming that the quadratic effect is moderated? How would such a moderation look like and how would it be interpreted?

If you have some clear answers or literature that can guide us on how to treat moderation and quadratic effects together, we are happy to implement this and allow both in one model.