Effect of the baryon-to-photon ratio and number of light neutrino species on the preferred value of α for the clocks model. Left and right panels correspond to the cases without and with the two priors discussed in the text; the one-sigma range corresponding to these priors is also shown for illustration purposes. It is important to notice the different axis ranges in the left and right panels for each case. In each panel, the parameters that are not displayed were marginalised. The 68.3, 95.4, and 99.7 percent confidence levels are plotted throughout.