The variance of a mean (sigma/sqrt(n)) declines with the sample size, so with grouped data I would want to specify the relative precision of each observation. Is there a way of doing this in BRMS?

I know that I can specify weights, but this multiplies the likelihood contribution of each datapoint and I’m not sure that would be appropriate. At least in a frequentist OLS context, repeating each mean n times would give very misleading standard errors.

I also considered the yi | se(sei) syntax on the left hand side of the formula, but this requires me to know sigma as well - while I only know the relative precision of the mean from each group.