I'm analyzing data from a twin study and wondered if OpenMx can test for the assumption that total variances of MZ and DZ pairs are not significantly different. Any suggestion on how to perform this test would be much appreciated!
Main menu
You are here
The OpenMx website will be down for maintenance from 9 AM EDT on Tuesday, September 17th, and is expected to return by the end of the day on Wednesday, September 18th. During this period, the backend will be updated and the website will get a refreshed look.
Printer-friendly version
The long and short of it is that you would fit a model to your data in which the phenotypic variances for MZ and DZ twins are two different free parameters, and then fit another in which the phenotypic variance is the same free parameter for both groups. The change in -2logL between the two models is a likelihood-ratio test statistic, asymptotically distributed as chi-square on one degree of freedom.
I'm attaching a script from the 2016 Boulder Workshop. You'll need to adapt it to your purposes, but hopefully it's enough to get you started.