  The statistical expectation values of the temperature fluctuations and
polarization of cosmic microwave background (CMB) are assumed to be preserved
under rotations of the sky. We investigate the statistical isotropy (SI) of the
CMB maps recently measured by the Wilkinson Microwave Anisotropy Probe (WMAP)
using the bipolar spherical harmonic formalism proposed in Hajian & Souradeep
2003 for CMB temperature anisotropy and extended to CMB polarization in Basak,
Hajian & Souradeep 2006. The Bipolar Power Spectrum (BiPS) had been measured
for the full sky CMB anisotropy maps of the first year WMAP data and now for
the recently released three years of WMAP data. We also introduce and measure
directional sensitive reduced Bipolar coefficients on the three year WMAP ILC
map. Consistent with our published results from first year WMAP data we have no
evidence for violation of statistical isotropy on large angular scales.
Preliminary analysis of the recently released first WMAP polarization maps,
however, indicate significant violation of SI even when the foreground
contaminated regions are masked out. Further work is required to confirm a
possible cosmic origin and rule out the (more likely) origin in observational
artifact such as foreground residuals at high galactic latitude.
