Participants scoring under 30 percent were dropped for misunderstanding

Evidence

Four participants’ data were excluded from the analysis as they achieved less than 30 % in at least one experimental block (chance level being 50 %), suggesting that they may not have understood the task correctly. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5290

Categorization

• QUESTION: Why does a score below 30 percent on a two-alternative task suggest the task was misunderstood rather than a genuine perceptual deficit? Chance is 50 percent, so sub-30 suggests systematic responding against the target, perhaps a reversed judgment criterion.