The issues in subjective test methodology are many. The experimenter must choose which scales to use and which assessors must understand the relative meaning of qualitative terms when appropriate and the intervals of the scale and, most importantly, must understand the nature of the information being sought (i.e., the question being asked). In video, an important issue concerns whether it is quality or degradation which is being assessed. This is a relevant issue in audio as well. Methods being studied include graphic scales and ratio scales. Graphic scales use previously-scaled qualitative terms, in a continuous manner, for assessment of quality. Ratio scales ask assessors to assign numbers, in proportion, to their quality judgments. On-going experiments with these methods will be discussed.
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