In the simplest sense, a measure is said to be valid to the degree that it measures what it is hypothesized to measure (Nunnally 1967, p. 75). More precisely, validity has been defined as the degree to which a score derived from a measurement procedure...

. An inference or an argument is valid if its conclusion follows deductively from its premises. The premises may be false, but if they are true the conclusion must be true. An inference is invalid if it is not valid. It is contravalid if an inference...

An intelligence test or examination rarely measures exactly what it is intended to measure. For example, a test of creativity might give results that are superficially plausible but which, on further investigation, turn out to be no more than a test of...

An expression of the capability of a scientific study to be able to identify or ascertain that which is being sought. This will depend primarily on the design of the study, the SENSITIVITY and SPECIFICITY of ascertainment techniques, and the conduct of...

The extent to which a test or other instrument measures what it is intended to...

The term validity as it occurs in logic refers generally to a property of deductive arguments, although many logic texts apply the term to statements as well (a statement is a sentence that “has a truth value,” i.e., that is either true or false)....