Please also provide the following information in addition to your question:
- Operating System: Ubuntu 18.04.1
- brms Version: 2.5.0
My aim is to fit a model within which I estimate a common slope for each group, and the deviation of each group to the common slope. However, I have only 4 groups, and I think it is counterproductive to use hierarchical prior on such a few groups (far longer estimations without real gain, imho). Could you enlight me about how to formulate this in brms?
y = intercepts + x + (x:groups)
But it produces a reference group, which I would prefer to avoid. Presenting a common slope and deviations would also be simpler than presenting the slopes of each groups separatly, to reveal common patterns.