What Is Discriminant Validity? | Definition & Example
Discriminant validity refers to the extent to which a test is not related to other tests that measure different constructs. Here, a construct is a behavior, attitude, or concept, particularly one that is not directly observable.
The expectation is that two tests that reflect different constructs should not be highly related to each other. If they are, then you cannot say with certainty that they are not measuring the same construct. Thus, discriminant validity is an indication of the extent of the difference between constructs.
Discriminant validity is assessed in combination with convergent validity. In some fields, discriminant validity is also known as divergent validity.
What is discriminant validity?
Discriminant validity is a subtype of construct validity. In other words, it shows you how well a test measures the concept it was designed to measure.
Discriminant validity specifically measures whether constructs that theoretically should not be related to each other are, in fact, unrelated.
For example, the scores of two tests measuring security and loneliness theoretically should not be correlated. In other words, individuals scoring high in security are not expected to score high in loneliness. If that proves true, these two tests would have high discriminant validity.
Discriminant validity is important because it shows you whether your test accurately targets the construct of interest or if it assesses separate, unintentionally related, constructs. This depends on the accuracy of your operationalization—i.e., your ability to turn abstract concepts into measurable variables or observations.
Discriminant vs. convergent validity
Discriminant and convergent validity help you establish construct validity. However, it’s important to keep in mind that they are not the same thing.
- Discriminant validity shows you that two tests that are not supposed to be related are, in fact, unrelated.
- Convergent validity shows you that two tests that are supposed to be related to each other are, in fact, related.
In other words, discriminant validity focuses on differences, while convergent validity focuses on similarities.
In order to show evidence of construct validity, a test should:
- Correlate with a test that is measuring the same or a related construct
- Not correlate with a test that is measuring a different construct
Researchers evaluate discriminant and convergent validity together. Both must be assessed in order to demonstrate construct validity. Note that it is important to assess convergent validity first, prior to discriminant validity.
Example of discriminant validity
You can establish discriminant validity in two ways:
- Picking completely opposite constructs (e.g., nervousness vs. confidence)
- Picking totally unrelated concepts (e.g., nervousness vs. favorite food)
How to measure discriminant validity
You can measure the discriminant validity of your test by demonstrating that there is no correlation or very low correlation between measures of unrelated constructs.
The degree of correlation is measured by a correlation coefficient, such as Pearson’s r. The value of the correlation coefficient always ranges between 1 and −1, and it serves as an indication of the strength and the direction of the relationship between variables.
Correlation coefficient values can be interpreted as:
- r = 1: there is perfect positive correlation
- r = 0: there is no correlation at all
- r = −1: there is perfect negative correlation
Although there is no consensus, a good rule of thumb is that high correlations between scales or scale items are considered problematic in terms of discriminant validity. A general rule of thumb when conceptualizing discriminant validity is that values starting at r = 0.85 are considered high.
Keep in mind that correlations with unrelated constructs should always be weaker than those of related constructs.
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Frequently asked questions about discriminant validity
- Why are convergent and discriminant validity often evaluated together?
- Convergent validity indicates whether a test that is designed to measure a particular construct correlates with other tests that assess the same or similar construct.
- Discriminant validity indicates whether two tests that should not be highly related to each other are indeed not related
You need to assess both in order to demonstrate construct validity. Neither one alone is sufficient for establishing construct validity.
- What is the definition of construct validity?
Construct validity is about how well a test measures the concept it was designed to evaluate. It’s one of four types of measurement validity, which includes construct validity, face validity, and criterion validity.
There are two subtypes of construct validity.
- How do I measure construct validity?
Statistical analyses are often applied to test validity with data from your measures. You test convergent validity and discriminant validity with correlations to see if results from your test are positively or negatively related to those of other established tests.
You can also use regression analyses to assess whether your measure is actually predictive of outcomes that you expect it to predict theoretically. A regression analysis that supports your expectations strengthens your claim of construct validity.
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