The choice of θ in the prior can be validated by checking its consistency with the optimal value of the KL divergence a posteriori. If we evaluate the prior for given θ and the corresponding optimal S KL value, then we expect a reasonably high value of the prior. That is, θS KL is of the order of one after refinement. If it is much larger, then the information from the experiment dominates the ensemble. We might have underestimated the quality of our ensemble or the size of the errors in the data. If it is much smaller, then the reference distribution dominates the ensemble. We might have overestimated the quality of our reference ensemble or the size of the errors in the data.