Hi,

I'm working on a PopPk model with a dataset that includes plasma samples from two different trials with different study designs. Plasma sampling was taken extensively before cmax in one study, but only three times before cmax in the other. I discovered that including Tlag improved model fit, and that including the impact of study design as a categorical covariate on Tlag had a significant impact, and that including it in the final model reduced OFV. I'm wondering if it's possible to have the model estimate Tlag for each study individually as two parameters (Tlag s1, Tlag s2) rather than including the impact as a covariate.

Thanks!