Similar to Fig. 8. Differences in the median values of ΔO/H between the interacting and control samples at different aperture sizes. In this case we compare using apertures in arcsec units with the differences in metallicity using different calibrators. Blue circles represent the differences obtained from the O3N2 revisited calibrator used in this study given in Marino et al. (2013). Red diamonds show the difference obtained from the calibrator presented by Pettini & Pagel (2004). The dashed line represent the difference reported by Ellison et al. (2008).