The gas kinetic temperature (plus symbols) and the column density (crosses) estimated from spectra with different signal-to-noise ratios. For each S/N ratio, the figure shows results from five realisations and their average as the dashed lines. The horizontal lines indicate the true values in the models. The three frames correspond to the default model (“def”), the σ_V-model, and the PEH model, respectively, of the 1.0 M_sun cloud.