Null tests for the cross-power spectra derived with the PCA N_fg = 4 (left panel), its weighted version PCAw N_fg = 4 (middle) and multiscale version mPCA N_L, N_S = 4, 8 (right). The WiggleZ galaxy maps have been shuffled along frequency (redshift). The thin blue lines show the spectra computed for 100 different shuffles. Empty blue diamonds correspond to the average and standard deviation across the shuffled samples, that we compare against (i) the reference spectra (filled orange circles) and (ii) the reference spectra with jackknife errors (filled green triangles). We use the solid orange and dashed green lines to show the best fits of the reference spectra, using Gaussian and jackknife errors respectively.