Distribution of observed Zeeman splitting (thick solid line) in the Effelsberg 6.7 GHz methanol maser sample. Over-plotted are models for the line of sight Zeeman splitting in the case of where the magnetic field is taken to have a Gaussian distribution with a Zeeman splitting dispersion of σ_Z in each dimension. Following a simple analysis, the best fitted model has σ_Z = 0.4 m s^-1 which would corresponds to a full 3-dimensional equivalent Zeeman splitting of  ⟨ ΔV_z ⟩  ≈ 0.62 m s^-1. As an indication, using the uncertain laboratory extrapolated g-factor (Sect. 3) this corresponds to  ⟨ |B| ⟩  ≈ 120 mG.