  In both WMAP and Planck observations on the temperature anisotropy of cosmic
microwave background (CMB) radiation a number of large-scale anomalies were
discovered in the past years, including the CMB parity asymmetry in the low
multipoles. By defining a directional statistics, we find that the CMB parity
asymmetry is directional dependent, and the preferred axis is stable, which
means that it is independent of the chosen CMB map, the definition of the
statistic, or the CMB masks. Meanwhile, we find that this preferred axis
strongly aligns with those of the CMB quadrupole, octopole, as well as those of
other large-scale observations. In addition, all of them aligns with the CMB
kinematic dipole, which hints to the non-cosmological origin of these
directional anomalies in cosmological observations.
