The most common definition of validity is typified by the question: are we measuring what we think we are measuring. There are four types of validity: face, content, criterion, and construct.
First is construct validity. It focuses on measuring concepts that are not directly observable and that we try to infer. For instance intelligence, anxiety or attitude. Rather than focusing on the tests themselves, the focus is on the meaning of the tests and its factors. Construct validity, then, is preoccupied with not just validating the test, but the theory, theoretical constructs, and scientific empirical inquiry (1). In addition, both convergence and discriminability are required.
- Convergence means that the evidence gathered all indicates the same thing (1).
- Discriminability means that it is possible to point out which measurements are not related to the construct.
- This is the most important form of validity because it connects measures with theories.
Criterion validity compares tests scores with one or more external variables or criteria that is known to measure the attribute of interest. There are two types of criterion validity: predictive and concurrent.
- Predictive validity focuses on future performance.
- Concurrent is at the same time.
- The information criterion validity provides is useful for new tests. However, its biggest challenge is the criterion used in the comparison.
- The information that these next two measures provide is mostly obvious. They require judgment and appearance.
Content validity focuses on the question: is the content of this measure representative of the universe of content of the property being measured. A test with high content validity would, in theory, be a representative sample of the universe of content. This type of validity relies on judgment. Some universes of content are easier to judge than others. For the obvious ones, content validity is assumed. For instance, a test of arithmetic to determine weather students can do additions.
Last is face validity, which focuses on looking to see if the measure obviously and clearly measures the intended measure. Measures are difficult to justify using face validity. However, it is the most basic and without it the rest of the validity methods would not work. For example, if we intent to measure a person’s ability to run, but we measure the number of pillows they own, face validity would indicate that this may not be an obviously valid measure.