Exchange bias (EB) effect has been vigorously researched for many years due to its possible applications in information storage and spintronics, especially in spin valves for magnetic recording devices. Even though many models have been expounded to this day, they do not prove convincingly the origins of EB effect. We attempt to establish the azimuthal dependence of EB effect with respect to varying the composition of the antiferromagnet CoxNi1-xO and temperature. In this report, we deposited the bilayer thin films of Ni0.8Fe0.2/CoxNi1-xO with x varying from 0.4 to 0.8 by magnetron sputtering and studied the variation of exchange bias field and coercivity. The EB effect was investigated for various external parameters such as temperature, the composition of antiferromagnetic layer, and the direction of magnetic field. The comparison between the calculations and experimental data showed good consistency with the spin glass model, and we suggest the validity of spin glass model to understand the origin of exchange bias effect in the Ni0.8Fe0.2/CoxNi1-xO bilayers.