When using sum contrasts for factors, the conditional effect (from
conditional_effects()) of the last level in the factor always has a particularly wide credible interval (see figure for an example). This happens independent of data and model.
Can someone shed light on this? (Might be related to this, but I am not sure: Extremely wide 95% CIs when using custom contrast coding)
[brms 2.12.0, R 3.6.2, macOS 10.15.4]