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

By *foswald*

Created *02/01/2011 - 17:30*

Tue, 02/01/2011 - 17:30 — foswald [1]

Hello! As the subject line states, I want to run a one-factor CFA with four indicators; however, when I run the model in OpenMx, I get -2 degrees of freedom. That makes sense because there are 6 correlations (given 4 indicators), and if I fix the factor variance to 1.0, I have to estimate 4 loadings and 4 error variances = 8 estimates, and we all know that 6 correlations - 8 estimates = -2 df.

However, we can constrain the estimation such that lambda-squared + error variance = 1.0 for each variable - how do I do this (I thought it would be automatic by virtue of using correlation, but probably a good thing that it is not)? Thanks! Fred

**Links:**

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

[2] http://openmx.psyc.virginia.edu/thread/867

[3] http://openmx.psyc.virginia.edu/thread/772

[4] http://openmx.psyc.virginia.edu/forums/opensem-forums/confirmatory-factor-analysis-and-measurement-models