I am trying to run an Individual Patient Metanalysis (IPD) in R. However, using a Random Intercept Model seems not to be appropriate since I only use 4 Trials.
In this article a stratified study intercept is proposed like this:
In a random effects model I would have fitted the model like this:
lmer(outcome ~ treatment + baseline + (1 + treatment | trial), data = data)
Can anyone help me get my head around implementing the stratified intercept instead of the random-effects model? I understand that the idea is to fit a model for every trial and use the trial-specific intercept, but I don't understand how to get it all together in the end.