Among various subjective quality evaluation methodologies, paired comparison has the advantage of improved simplicity of the subjects'evaluation task due to simplified rating scales and direct comparison of two stimuli. Thus, it may lead to more reliable results when individual quality levels are difficult to define, quality differences between stimuli are small or multiple quality factors are involved. This paper proposes a new method to analyze results of paired comparison-based subjective tests. By assuming that ties convey information about significant differences between two stimuli being compared, the confidence intervals for the quality scores are estimated using a maximum likelihood criterion, which enables us to intuitively examine the significance of quality score differences. We describe the complete test methodology including the test procedure, outlier detection and score analysis applied to quality assessment of 3D images acquired using varying camera distances. Experimental results demonstrate the usefulness of the proposed analysis method, as well as the enhanced quality discriminability of the paired comparison methodology in comparison to the conventional single stimulus methodology.