Streetlight effect
Etymology
The name comes from an old joke, told of the folk sage Nasreddin among others: a man searches for lost keys under a streetlight, not because he dropped them there, but “because this is where the light is.” Social scientists adopted “the streetlight effect” as a label for this observational bias.
noun phrase · /STREET-lite ih-FEKT/
The tendency to search for answers where it is easiest to look rather than where the answer actually lies.
What it names
The bias of studying the measurable and convenient — because the data is there — instead of the relevant.
Example
Studying only the data a company already collects is a streetlight effect that can miss the real cause of the problem.
Related idea
The streetlight effect is looking where it is easy; the Texas sharpshooter fallacy is drawing the target around wherever the shots happened to land — both let convenience masquerade as evidence.