Panel a: marginal posterior distributions for ξ_E conditional on data, D, and models, M_R (red), and M_A (green). Panel b: marginal posterior distribution for R₀ conditional on data, D, and model, M_A. The data, D, consist of the collective use of the CoMP data set analysed by Verth et al. (2010). The posterior summaries are for p(ξ_E|M_R, D), for p(ξ_E|M_A, d), and for p(R₀|M_A, D), with the uncertainty given at the 68% credible interval. The posteriors are computed by Markov chain Monte Carlo sampling using the Python emcee package (Foreman-Mackey et al. 2013).