Symmetric two-sided scales are needed when processing may improve a signal

Evidence

In situations in which the processed signal could be evaluated as being either better or worse, a comparison category-rating (CCR) test can be used. Its rating scale is shown in Table 7.3, and it can be seen that it is a symmetric two-sided scale. Listeners are asked to rate the two signals presented in terms of the quality of the second signal relative to the first. The CCR test might be used if one is interested in the effect of a signal-processing methodology being applied to an audio signal, such as noise reduction, in terms of whether it has improved the original signal. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2395

Categorization

• DEFINE: Explains the CCR test and why a two-sided scale is required when either improvement or degradation is possible.
• XREF: connects to: Scales with high Cronbach-α may still conceal several distinct latent factors. — Ruiqian Li and Paul Froese, The Duality of American Christian…, 84