Correlation between the Stokes parameters from Planck (Q_s, U_s) and the fractional Stokes parameters from RoboPol (q_v, u_v). The blue points represent the correlation between U_s and u_v, while the orange points show the correlation between Q_s and q_v. The blue dashed line indicates the best-fit line of the joint correlation determined by minimizing χ², while the solid blue and solid orange lines correspond to the U_s − u_v and Q_s − q_v fits, respectively. The black dashed line corresponds to the value from Planck Collaboration XII (2020).