(a) Comparison of Hα luminosity of 54 isolated compact H ii regions common in this study and Scoville et al. (2001). The mean value of the differences is Δlog  L (This study − Scoville et al. (2001)) = 0.03 ± 0.12 (solid line). (b) Comparison of Hα luminosity of 164 isolated compact H ii regions common in this study and Gutierrez et al. (2011). The mean value of the differences is Δlog  L (This study − Gutierrez et al. (2011)) = 0.01 ± 0.07 (solid line).