Distributions of the SED fitting results showing the contamination of the continuum at Hβ by evolved stars. Left. Distribution of the correction factor f_r values given by equation 1. The distribution peaks at f_r= 1.1–1.2, indicating that while all the HII galaxies in this sample have significant underlying old and intermediate-age stellar populations, for most galaxies the effect in EW(Hβ) is seen to be below 50%. Right. Histograms of the distribution of observed EW(Hβ) in black, and corrected (Young) in blue using SED fitting. The distribution of ages [EW(Hβ)] of the young stellar populations is seen to be much flatter than the distribution of observed equivalent widths.