Intensity of He II/Hβ as a function of f_esc(LyC) (left) and 12 + log(O/H) (right) for different SDSS stacks (circles). The left panel shows the four stacks in bins of f_esc(LyC) (very strong, strong, weak, and nonleakers in blue, green, yellow, and red, respectively), and the right panel shows the nine stacks in bins of f_esc(LyC) and 12 + log(O/H) (12 + log(O/H)< 8.0, 8.0–8.3, and > 8.3, in blue, green, and red, respectively). Details of the definition of stacks can be found in Table 1. x-values and horizontal error bars refer to the mean and 68% confidence intervals (bootstrap resampling) of f_esc(LyC) and 12 + log(O/H) measured for each bin (Table 1). Individual sources with X-shooter observations are also shown (empty squares; LzLCS sources and five LyC emitters were analyzed in Guseva et al. 2020). Upper limits for SDSS stacks and X-shooter observations refer to 2σ limits. The right panel also shows observations (plusess) of a compilation of almost 900 star-forming galaxies from Izotov et al. (2016a) (average and standard deviation marked with a solid line and region, respectively).