[R-sig-ME] Mixed Model Version of Two-Stage Least Squares Analysis

[Paul Miller]

Hello Everyone,

I'm familiar with the use of Two-Stage Least Squares Analysis to obtain results like one gets with SEM. I was wondering if anyone knows how to extend this approach to nested data. My data contain multiple observations from cancer patients. The number of observations varies by patient and the intervals between observations are not equally spaced.

Is it possible to apply a 2SLS approach to my data? If so, are there measures of model fit from the standard 2SLS approach that will work if I'm using a mixed model to account for non-independence of observations in my data? Or are there maybe some other measures I could use?

Thanks,

Paul