Number of sources in each 10-degree Galactic longitude interval. The gray and black-line columns represent the full sample of the methanol masers (Pestalozzi et al. 2005) and the fraction covered by our sample, respectively. Overlaid inset panel: distributions of the maser intensities for the sampled and missed sources in l = 10° to 50° range. For each statistical box, the entire error bar (whisker) represents the overall distribution, the box and its inner segment represent the 25% to 75% range and the median value, respectively.