Comparison of observed ionic number ratios ⟨ S^{3 +} ⟩ / ⟨ S^{2 +} ⟩ and ⟨ Ne^{2 +} ⟩ / ⟨ Ne⁺ ⟩ to the corresponding results from our model H ii regions. The triangles represent H ii regions in the metal rich galaxy M 83 (gray, values from Rubin et al. 2007) and M 33 (cyan triangles, values from Rubin et al. 2008); the circles represent model H ii regions using as ionizing sources dwarf stars with temperatures from 35 000 K to 55 000 K and metallicities of 0.1 Z_⊙ to 2.0 Z_⊙. The lower metallicities are correlated with a larger fraction of the higher ionization stages both in the observations and the synthetic H ii region models.