moderated curvilinear effects

[Na Zhao]

Hi everyone,

I am doing a moderated curvilinear effects with the following code:

mixed DV c.IV##c.IV##c.MV ||ID

could I ask how to check the slopes and p values of the curvilinear effects when the moderator is high (+1SD) v.s? Low (-1 SD)?


For linear effects, i know we can use margins, dydx(X) at (Moderator ($h $l) vsquish post,

but I think dydx would not work for curvilinear effects. So which syntax should i use to check the curvilinear effects when moderator are low and high? thanks so much

[Clyde Schechter]

summ IV
local high = r(mean) + r(sd)
local low = r(mean) - r(sd)

margins, dydx(IV) at(MV = (`high' `low')

This will give you the marginal effects of MV at both of those value of IV, and it takes into account both the linear and quadratic terms in IV. I do not know what you mean by the "slopes and p-values of the curvilinear effects." There are no meaningful statistics that derive only from the non-linear terms in the model: in polynomial models only the joint effects of terms of all degree are meaningful.

Edited to correct error in code.