Validity Types In Searches: Content Validity

In statistical terms, validity is defined as the proportion of the true variance that is relevant for the purposes of the test. With the term ‘relevant’, we understand what is attributable to the variable, to the characteristics measured by the survey (1). Did you know that there are several types of validity? Next, we’ll talk specifically about content validity.

The validity of a test is usually defined by:

• The relationship between your scores with some measure of external criteria or;
• The extent to which a test measures a hypothetical underlying characteristic or “construct”.

Validity in psychometric terms

In psychometric terms,  validity is a concept that has gone through a long evolutionary process. In the beginning, Muñiz (1996) adopted the validity with a specific position. He held that “a test is valid for what it correlates with.”

Validity is now understood as an  overall evaluative judgment. In this judgment, empirical evidence and theoretical assumptions support the sufficiency and appropriateness of interpretations not only of the items, but also of the way people respond, as well as the context of the assessment.

Therefore, what is validated is not the test. What is specifically validated are the inferences made from it. This has two consequences:

• The person responsible for the validity of a test is no longer just its constructor, but also the user.
• The validity of a test is not established once and for all. It is the result of the accumulation of evidence and theoretical assumptions that occur in an evolutionary and continuous process. This includes all experimental, statistical, and philosophical questions by which scientific hypotheses and theories are evaluated (3).

In this context, the concept of  validity refers to the adequacy, meaning and usefulness of the specific inferences made with the test results. Validation of a test is the process of accumulating evidence to support those inferences. Thus, validity is a unitary process. Although evidence can be accumulated in various ways, validity always refers to the degree to which this evidence supports the inferences made from the scores (4).

Evidence Types

In 1954, a committee chaired by LJ Cronbach established, at the request of the American Psychological Association (APA), that validity had four types. These are:

• Content validity.
• Predictive validity.
• Concurrent validity.
• Construct validity.

Currently, it is agreed, from a scientific point of view, that  the only admissible validity is the construct validity  (Messick, 1995).

Validity and its aspects

In the study of validity, the evidence is related to five aspects :

• Content  (the relevance and representativeness of the test).
• Noun  (the theoretical reasons for the observed consistency of responses).
• Structural  (internal configuration of the test and  dimensionality ).
• Generalization  (the degree to which the inferences made in the test can be generalized to other populations, situations, or tasks).
• External (relationships of the test with other tests and constructs).
• Consequence (ethical and social consequences of the test) (3).

Thus, within this validity, we can understand other types of validity or strategies. As mentioned earlier, they are content validity, predictive validity, concurrent validity and construct validity.

Validity Types: Content Validity

In this type of validity, the following question is answered: the items that make up the test are really a sample representative of the domain content or behavioral domain that interests us?

For the sake of understanding, a  behavioral domain or field is a hypothetical grouping of all possible items that cover a specific psychological area. For example, a vocabulary test should be an adequate sample of possible mastery of items in that area.

In this sense, the  content validity is a “measure” the adequacy of sampling. The “measure” is enclosed in quotation marks because this type of validity consists of a series of estimates or opinions. These estimates do not provide a quantitative index of validity. (1)

This type of validity is mainly associated with performance tests (math test, history…). For its determination, the test questions are systematically compared with the behavioral domain of the postulated content.

For example, we have a list of 500 words that we hope students in a course can spell correctly. Therefore, performance against these words will be uniquely important to test the student’s ability to correctly spell the 500 words. However, the test will only have content validity as long as an adequate sample of the 500 words it represents is provided. (1)

If we select  only easy or difficult words, or words that represent only certain types of spelling errors, we will likely get  very low content validity.

Conclusion: what is the use of content validity?

The main aspect of content validity is the sampling of items. In other words, content validity is able to determine whether the sample of its items is representative of the universe or behavioral domain of the item it supposedly represents (1).

Therefore, content validity is the type of validity linked to the test itself and what it intends to measure. For example, it will let us know if the sample of test items is representative of the math domain we want to assess. It is, therefore, an important concept both in statistics and in the use of psychological or performance tests.

In conclusion, the validity study is an analysis of a metric test; in our case, since we are talking about psychology, psychometric, whose conclusions refer to the degree to which the referred test measures what we want to be measured. Logically, the more validity a test has, in the absence of other analyzes – such as reliability -, the better it will be.