Percent deviation (log scale) between the absorption at 0.3 keV produced by a lognormal distribution of column densities and a single-parameter absorption model (i.e., tbabs (N_H = avg_Θ)) as a function of the free parameters avg_Θ and std_Θ. Blue and red points show the scatter plot for distributions extracted from 6′×6′ random regions in the Galactic center column density map (Molinari et al. 2011) and 1deg × 1deg random region at Galactic latitudes b > 10deg from the HI column densities of HI4PI Collaboration (2016), respectively.