Data-driven purity ($P$) estimates of the electron sample after applying TPC and EMCal electron identification criteria as a function of $p_{\rm T}$ in pp collisions at $\sqrt{s}=$ 13 TeV (left) and in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=$ 5.02 TeV (right). The boxes indicate the systematic uncertainty arising from the use of different scaling ranges for the hadronic background.