Conjunction fallacy

Common card · No. 286408

A conjunction effect or Linda problem is a bias or mistake in reasoning where adding extra details (an "and" statement or logical conjunction; mathematical shorthand: ∧ {\displaystyle \land } ) to a sentence makes it appear more likely. Logically, this is not possible, because adding more claims can make a true statement false, but cannot make false statements true: If A is true, then A ∧ B {\displaystyle A\land B} might be false (if B is false). However, if A is false, then A ∧ B {\displaystyle A\land B} will always be false, regardless of what B is. Therefore, A ∧ B {\displaystyle A\land B} cannot be more likely than A.

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