Effects of varying the sample purity on the estimated Lyα LF. Top: Colored squares show different realizations of our Lyα LF in the range z = 2.0 − 3.8, obtained after scaling the number of true positives in the purity computation by a factor ρ = 0.1, 0.5, 1.0, 1.5, 2.0. We also show the mock QSO LF for each ρ (solid lines). We show the uncertainties of the LF with ρ = 1. The variation of the LF is inside the 1σ errors for all the shown values of ρ. Bottom: Estimated purity for the different values of ρ.