I am using Simbiology for population pharmacokinetic model development. I use non-linear mixed effect modelling approach. I have a doubt in the intial assignment of data type in the dataset.
Suppose I have age and gender in the dataset. Clearly, I will assign age as covariate. Now gender is also a covariate. But there is a option in the dataset type which is group variable.
Now I am confused on whether I should assign gender as covariate or group variable.?
I am attaching a screenshot for the reference.