T–T plots for Stokes Q and U maps of the COSMOGLOBE DR1 K- band versus the COSMOGLOBE DR1 30 GHz (black) and the WMAP9 K- band versus Planck PR3 30 GHz pixels (red) for all regions. The horizontal (solid and dotted) lines indicate the corresponding inverse variance weighted values of the spectral index, averaged over rotation angle, and in the COSMOGLOBE case also weighted over samples. The corresponding β_s values can be found in Fig. 8.