Parameter probability distribution obtained with the check-up of MCMC analysis on the step function. The red solid line represents the median of the distribution, the red dotted lines correspond to the 1 − σ uncertainties assuming a Gaussian distribution. The solid green line represent the maximum of the likelihood solution while the solid orange correspond to the initial input parameters that the check-up should recover. Only a small fraction of the sampler is displayed to avoid overweighted figures, however, the histograms were constructed with the full sample.