On the whole, the posteriors for all of the species are symmetric, with the exception of OH*, O*, CO and CH 3 . It is quite surprising that these species are the only ones with asymmetric posteriors, which are quite common in similar studies due to the complex and nonlinear dependence of reaction rates on the species enthalpies. For some species, the lack of skewness and kurtosis in the posterior can be explained by examining the sensitivities of the species within the model. In general, physisorbed hydrogen (H 2 *) and methane (CH 4 *), along with adsorbed carbon (C*), methylidine (CH*), and formyl (CHO*) have little e↵ect on the outlet molar flow rates or model observables. Figure shows the first order sensitivities of the methane conversion to all of the species in the model. The sensitivity plots for a number of other observables (CO/CO 2 selectivity, O 2 conversion, etc.) can be found in the supplementary material, but overall a lack of sensitivity to these species was observed for all benchmarks used. Since the model is insensitive to these species, their posterior distributions are very similar to their prior distributions.