TOS 8

Claims about audio quality can ultimately only be justified by scientifically reproducible perceptual tests. Agreement on that fact is what makes hydrogenaudio-- and any reasoned discussion about audio-- possible. This principle has been enshrined in the eighth article of hydrogenaudio's Terms of Service:

All members that put forth a statement concerning subjective sound quality, must -- to the best of their ability -- provide objective support for their claims. Acceptable means of support are double blind listening tests (ABX or ABC/HR) demonstrating that the member can discern a difference perceptually, together with a test sample to allow others to reproduce their findings. Graphs, non-blind listening tests, waveform difference comparisons, and so on, are not acceptable means of providing support.

A test of audio quality is scientific only if it is blind. This eliminates the effects of pre-existing opinions, the placebo effect, and other psychological biases so we can consider the audible differences.

Test results are convincing only when they have been shown to be reproducible. A single blind test, while a useful data point, doesn't constitute convincing evidence. Even a single listener's responses to perceptual tests will vary from moment to moment, so a single result could be "due to chance" rather than showing a real quality difference. Statistical methods-- both frequentist and Bayesian-- can help us recognize convincing evidence when we combine the results of multiple observations.