Marginalized probability distributions for τ_c (top) and (bottom). Different colours correspond to different levels of uncertainty in the a priori estimate of R_p (ΔR_p), as stated in the legend. All panels share the same legend. From left to right: no-cloud, thin-cloud, and thick-cloud scenarios. As discussed in the text, a plateau in the marginalized probability distribution entails that only an upper or lower limit can be set.