  We systematically investigated the anisotropic in-plane resistivity of the
iron telluride including three kinds of impurity atoms: excess Fe, Se
substituted for Te, and Cu substituted for Fe. Sizable resistivity anisotropy
was found in the magneto-structurally ordered phase whereas the sign is
opposite ($\rho_a$ $>$ $\rho_b$, where the $b$-axis parameter is shorter than
the $a$-axis one) to that observed in the transition-metal doped iron arsenides
($\rho_a$ $<$ $\rho_b$). On the other hand, our results demonstrate that the
magnitude of the resistivity anisotropy in the iron tellurides is correlated
with the amount of impurities, implying that the resistivity anisotropy
originates from an exotic impurity effect like that in the iron arsenides. This
suggests that the anisotropic carrier scattering by impurities is a universal
phenomenon in the magneto-structurally ordered phase of the iron-based
materials.
