In stereoscopic 3D video, it is known that humans can perceive high quality 3D video provided that one of the views in high quality. Hence, in stereo video encoding the best overall rate vs. perceived-distortion performance may be achieved by asymmetric coding which is reduction of the spatial or quantization resolution of the auxiliary view, while keeping the reference view in full resolution. In this paper, we propose an interactive quality assessment method to evaluate perceptual quality for asymmetric coding of 3D video. Subjective Evaluation of Stereo VIdeo Quality (SESVIQ) is proposed as stereo extension of SAMVIQ (Subjective Assessment Methodology for VIdeo Quality) methodology of EBU. We conducted subjective experiments to compare different algorithms such as symmetric over asymmetric rate allocation or spatial over SNR (signal-to-noise ratio) scaling of the auxiliary view. Test results show that the interactive test methodology gives more reliable results than conventional sequential test methodology, especially for low bitrate scenarios.