Judging a class by only its detectable members: all toupees look terrible, because the convincing ones are not counted as toupees.
The sample available to an observer is the failures, because success in this class consists of not being noticed. The error is general and shows up wherever competence is invisible by definition: good editing, good security, good administration and good acting are all judged from the instances that failed.
In practice
- An IT department is judged on the outages, since the years without one produce no evidence of anything.
- A reader who concludes that translations are clumsy has read the clumsy ones and not noticed the rest.
- Standing
- A folk statement of selection bias on an unobserved population. Compare survivorship bias, which selects on outcome rather than on detectability.
- Subject
- Decision-making & Reasoning
- Essay
- The catalogue of predictable errors