Comparison of the α values estimated using the ACF and APS estimators (black dots). The columns from left to right show estimates from lower to higher redshift ranges, with average ⟨z⟩ = 0.172, ⟨z⟩ = 0.270, and ⟨z⟩ = 0.386. The first row shows results for the 21 cm only analyses, and the middle and bottom rows show results including white noise only and white noise + foreground residual, respectively. The red dots in the bottom row show α estimates from the reconstructed (foreground cleaned) maps.