I am trying to fit an ACE model on a latent variabel using path specification. I started out with a twin model in which each individual has one common factor explaining the variance on 7 observed variables. These factors are obviously correlated within an MZ or DZ pair. I am now removing this correlation between twins and adding a ACE decomposition of the factor variance. Basically i am fitting a common pathway model.
My first try was to restric the factor variance to 1, but since i added A C and E to explain the factor variance this will not work. In order for this to work i need to restrict the total variance for a^2 + c^2 + e^2 to 1. This seems like the only practicle way for me to scale the model.
how do i implement this restriction in a path specification model?
The model i am using basically is equal to the ACE example in the tutorial except that i am decomposing variance for a latent variable instead of an observed variable. Can this be done using OpenMX?
Any sugestions are welcome