Construct validity

In social science and psychometrics, construct validity refers to whether a scale measures the unobservable social construct (such as "fluid intelligence") that it purports to measure. It is related to the theoretical ideas behind the personality trait under consideration; a non-existent concept in the physical sense may be suggested as a method of organising how personality can be viewed. The unobservable idea of a unidimensional easier-to-harder dimension must be "constructed" in the words of human language and graphics.

A construct is not restricted to one set of observable indicators or attributes. It is common to a number of sets of indicators. Thus, "construct validity" can be evaluated by statistical methods that show whether or not a common factor can be shown to exist underlying several measurements using different observable indicators. This view of a construct rejects the operationist past that a construct is neither more nor less than the operations used to measure it.

Evaluation of construct validity requires examining the correlation of the measure being evaluated with variables that are known to be related to the construct purportedly measured by the instrument being evaluated or for which there are theoretical grounds for expecting it to be related (Campbell & Fiske, 1959). Correlations that fit the expected pattern contribute evidence of construct validity. Construct validity is a judgment based on the accumulation of correlations from numerous studies using the instrument being evaluated.

There are variants of construct validity:
 * convergent validity,
 * discriminant validity, and
 * nomological validity.