Biased Evidence
LSAT glossary · Reading Comprehension
Definition
A reasoning flaw in which the supporting evidence comes from a sample, source, or context that is systematically unrepresentative of the population the conclusion describes. Classic LSAT example: a poll of Sports Illustrated readers used to conclude something about "the world" — SI readers skew American, English-speaking, and toward sports SI covers, so they cannot ground claims about global recognition. The flaw includes self-selected samples, survivorship bias, and any evidence gathered under conditions different from the conclusion's context.
Biased Evidence in plain English
Biased evidence means the proof you're leaning on came from a lopsided source, so it can't fairly speak for the bigger group the conclusion is about. Imagine deciding "everyone's favorite food is nachos" after polling only people leaving a nacho stand — of course they love nachos; that's why they were there. The classic version is a survey of Sports Illustrated readers used to claim something about "the whole world," even though those readers skew American, English-speaking, and sports-obsessed. The tip-off is a mismatch: the sample was gathered under narrow conditions, but the conclusion sweeps far wider than the sample can honestly support.
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