Validity for design vs. validity for measurement

Solution Preview

Concept of validity for measurement
This concept is based on data collection and/or statistical analysis. Here, the term refers to the degree to which a study supports the intended conclusion drawn from the results. In the Campbellian tradition, this refers to the degree of support for the conclusion that the causal variable caused the effect. A list of the validity types that are typically mentioned in texts and research papers when talking about the quality of measurements include:

Construct validity
Construct validity refers to the totality of evidence about whether a particular operationalization of a construct adequately represents what is intended by theoretical account of the construct being measured. (Demonstrate an element is valid by relating it to another element that is supposedly valid.)

There are two approaches to construct validity- sometimes referred to as 'convergent validity' and 'divergent validity' (or discriminant validity).

Convergent validity
Convergent validity refers to the degree to which a measure is correlated with other measures that it is theoretically predicted to correlate with.

Discriminant validity
Discriminant validity describes the degree to which the operationalization does not correlate with other operationalizations that it theoretically should not be correlated with.

Content validity
Content validity is a non-statistical type of validity that involves "the systematic examination of the test content to determine whether it covers a representative sample of the behaviour domain to be measured" (Anastasi & Urbina, 1997 p. 114).

A test has content validity built into it by careful selection of which items to include (Anastasi & Urbina, 1997). Items are chosen so that they comply with the test specification which is drawn up through a thorough examination of the subject ...