[R] LMMs with some variance terms forced constant

[Erica E.M. Moodie, Dr.]

Hello,

I have been asked to help perform a meta-analysis with individual- and aggregate-level data. I found a nice article on this, and the idea is easy to understand: use a mixed effects models, but for the studies where there is only aggregate level data, force the variance to be that which was observed. Unfortunately, I am struggling to see how to implement this in R. I am familiar with "standard" mixed model formulations using nlme and lmer, but not able to see how to force this specific variance structure on my model so that some variance terms are not estimated.

Thanks for your time and any advice.

Best wishes,
Erica



Erica Moodie
Associate Professor, Biostatistics
Biostatistics Program Director
Department of Epidemiology, Biostatistics, & Occupational Health
McGill University
http://www.biostat.mcgill.ca/moodie


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