Results for NGC 625. Panel a: comparison of the observed (losange) and predicted intensities for our best-fitting single (blue bar) and mixed (red bar) H II region+PDR models. Lines are sorted by decreasing energy. The fitted lines have labels in boldface. Panel b: for mixed models: respective contributions from component #1 and component #2 to the line prediction. For PDR lines ([C II], [O I], and [Si II]), only the contribution from the ionized gas is shown; the PDR contribution is one minus the sum of the contributions from the plot. Contributions are expected to be dominated by one or the other component if their model parameters are noticeably different. Panel c: probability density functions of the model parameters (n_H, U, cov_PDR/scaling factor) for single (left panel) and mixed (right panel) models. The scaling factor corresponds to the proportion in which we combine two models in the mixed model case. It is equal to unity otherwise. It is shown with dashed lines in the same panels as the PDR covering factor. Vertical dotted lines show values of the best-fitting model. Black asterisks show the range and step of values of the grid parameters.