How to add covariates in Mixed Effect Analysis?

Dear Dr. Yan,

I encountered a problem while doing Mixed Effect Analysis. I wanted to add covariates (age, gender and handness). But the problem is that the covariates are the same for both condition 1 and condition 2.

I added as





Then Dpabi ran for hours and gave weired results. I also tried to name the covariates differently but it didn't work either. I wonder what is the proper way to add covariates in Mixed Effect Analysis. 

Thank you!

Best Regards,




Do not add these covariates (age, gender and handness).

You can add covarite of head motion as this is different between conditions.

In mixed effect analysis, the between subject variance would be taken out, thus no need for between subject covarites (e.g., age, gender and handness)