The sensitivity of the distribution p (y|c) of the observables to a particular force-field parameter c determines its impact on the respective energy uncertainty, an issue examined in detail in Bayesian inference of force fields (BioFF). 33 p (y|c) is defined analogously to Eq. ( ) with p(x) now paramaterized by c, i.e., p(x|c) ∝ exp[-βU (x|c)] through the potential energy U (x|c). The reference ensemble is defined by c = c 0 . To lowest order, the KL divergence S KL (c) grows quadratically with small changes δc = c -c 0 in the force-field parameter c,