Hey everyone,

I am doing probit regressions with Stata 14.1 and I want to get average marginal effects for the variables age and age squared. I tried two different ways:

1)
Code:
probit y c.age c.age2 x3 x4 ...
margins, dydx(*)
2)
Code:
probit y c.age##c.age x3 x4 ...
margins, dydx(*)
In 1) i get two different results for age and age2, whereas I only have one result for age (in total) in 2).

Why is there only one result in 2) and which notification would be appropriate to identfy an effect that is u-shaped for age?

Thanks a for any suggestions! :-)