I am running an experiment in which each participant completes a task that has two conditions (within subject). I am fitting a hierarchical model that fits a parameter to each condition, beta1 for condition 1 and beta2 for condition 2. I would like to make a within-subject comparison between the betas for the two conditions. Is there a way to achieve this in stan? I can take the posterior draws for beta1 and beta2 for each participant, subtract them, and generate the HDI for the difference for each participant, but I’m not sure how to proceed from there if I want a pairwise comparison in the sample with all participants.