Simulation sample of the QSO Lyα forests. The transmission e^−τ is shown in the top panel. The lower four panels are the Poisson sampling of flux F_ce^−τ plus noise with (1) ﹩F_{c}=2000﹩, (2) ﹩F_{c}=2000( \lambda / \lambda _{0}) ^{2}﹩, ﹩\lambda _{0}=4133﹩ Å, (3) ﹩F_{c}=2000[ 1+0.1\mathrm{sin}\,[ 2\pi ( \lambda -\lambda _{\mathrm{min}\,}) / ( \lambda _{\mathrm{max}\,}-\lambda _{\mathrm{min}\,}) ] ﹩, and (4) ﹩F_{c}=2000[ 1+0.5\mathrm{sin}\,[ 2\pi ( \lambda -\lambda _{\mathrm{min}\,}) / ( \lambda _{\mathrm{max}\,}-\lambda _{\mathrm{min}\,}) ] ﹩, respectively.