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  2. Validity (logic) - Wikipedia

    en.wikipedia.org/wiki/Validity_(logic)

    The corresponding conditional of a valid argument is a logical truth and the negation of its corresponding conditional is a contradiction. The conclusion is a necessary consequence of its premises. An argument that is not valid is said to be "invalid". An example of a valid (and sound) argument is given by the following well-known syllogism:

  3. Validity (statistics) - Wikipedia

    en.wikipedia.org/wiki/Validity_(statistics)

    [1] [2] The word "valid" is derived from the Latin validus, meaning strong. The validity of a measurement tool (for example, a test in education) is the degree to which the tool measures what it claims to measure. [3]

  4. Logical consequence - Wikipedia

    en.wikipedia.org/wiki/Logical_consequence

    A valid logical argument is one in which the conclusion is entailed by the premises, because the conclusion is the consequence of the premises. The philosophical analysis of logical consequence involves the questions: In what sense does a conclusion follow from its premises? and What does it mean for a conclusion to be a consequence of premises ...

  5. Test validity - Wikipedia

    en.wikipedia.org/wiki/Test_validity

    Test validity is the extent to which a test (such as a chemical, physical, or scholastic test) accurately measures what it is supposed to measure.In the fields of psychological testing and educational testing, "validity refers to the degree to which evidence and theory support the interpretations of test scores entailed by proposed uses of tests". [1]

  6. Validity - Wikipedia

    en.wikipedia.org/wiki/Validity

    Validity (statistics), the degree to which a statistical tool measures that which it is purported to measure Statistical conclusion validity, establishes the existence and strength of the co-variation between the cause and effect variables

  7. Proof by contradiction - Wikipedia

    en.wikipedia.org/wiki/Proof_by_contradiction

    Its negation ¬H(M) states that "M neither halts nor does not halt", which is false by the law of noncontradiction (which is intuitionistically valid). If proof by contradiction were intuitionistically valid, we would obtain an algorithm for deciding whether an arbitrary Turing machine M halts, thereby violating the (intuitionistically valid ...

  8. First-order logic - Wikipedia

    en.wikipedia.org/wiki/First-order_logic

    A formula is logically valid (or simply valid) if it is true in every interpretation. [22] These formulas play a role similar to tautologies in propositional logic. A formula φ is a logical consequence of a formula ψ if every interpretation that makes ψ true also makes φ true. In this case one says that φ is logically implied by ψ.

  9. Satisfiability - Wikipedia

    en.wikipedia.org/wiki/Satisfiability

    For example, the formula + = is satisfiable because it is true when = and =, while the formula + = is not satisfiable over the integers. The dual concept to satisfiability is validity ; a formula is valid if every assignment of values to its variables makes the formula true.