Hi, I have a question for Gang.

I have a skewed quantitative variable I am trying to include in my model. The variable is a factor score from a CFA, and has a mean of 0.05, but it is very heavily skewed. Following are pictures of its boxplot and histogram. I am trying to model a dataset of twins, so I have to use 3dLME. I have two questions:

- Is 3dLME robust to violations of normality in quantitative variables? If not, what are some transformations we can do to the data in order to make it work?
- When we specified the CFA, we fixed means at 0 and residual variances at 1. Our thought initially was to specify the centering at 0. But given the skewness of this variable, should we be taking a different approach to thinking about centering?

https://i.imgur.com/EftlmdI.png

https://i.imgur.com/k3lX3Yb.png

Thank you very much!!