Hello all,

I am attempting to fit a mixed effects model to some longitudinal secondary data. The variables in question are an ordinal variable with 6 levels and participant test scores. The relationship between the variables is nowhere near linear, and the test scores also violate the assumption of normally distributed residuals.

I know that I could conduct a poisson regression to account for the non-normal distribution, but my data still violates the assumption of linearity, which poisson also requires. I had thought about using the new menl command, which allows us to fit non-linear mixed effects models, but I've run into two issues: firstly, I'm not sure that this would be appropriate with non-normally distributed residuals, and secondly, I've been unable to find clear guidance on how to use menl.

I would very much appreciate any guidance that the stata experts here can offer! Please, do let me know if I need to provide any further information.

Aimee