Published on *OpenMx* (http://openmx.psyc.virginia.edu)

By *MNivard*

Created *01/25/2011 - 10:49*

Tue, 01/25/2011 - 10:49 — MNivard [1]

Hi all,

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

**Links:**

[1] http://openmx.psyc.virginia.edu/users/mnivard

[2] http://openmx.psyc.virginia.edu/thread/851

[3] http://openmx.psyc.virginia.edu/thread/820

[4] http://openmx.psyc.virginia.edu/forums/opensem-forums/behavioral-genetics-models