Validity refers to a test’s ability to measure what it is supposed to measure. Learn more about the different types of validity and why they are important, and test your knowledge with a quiz.
Imagine that you are a psychologist working in your office. Your client comes in and tells you that he thinks he is suffering from anxiety.
You decide that before you proceed with treatment and diagnosis, you need to administer a psychological assessment.You search through your drawer of tests and find the Beck Anxiety Inventory (BAI). The first question you ask yourself is ‘What does the BAI measure?’ You read the test manual, which notes that the BAI is used to assess the level of anxiety for adults and adolescents.
The second question that you ask yourself is related to the validity of the BAI, or how well the BAI measures what it was designed to measure. To answer this question, we will look at three different subdivisions of validity: construct validity, content validity, and criterion validity.
You are probably already familiar with the definition of a construct. A construct is an attribute, skill, or ability that is based on established theories and exists in the human brain. Intelligence, anxiety, and depression are all examples of constructs. Construct validity is the degree to which a test measures the construct that it is supposed to measure.
In other words, how well does the BAI measure the theoretical concept of anxiety? Establishing construct validity involves looking at numerous studies that use the BAI. There are two necessary components of construct validity: convergent and discriminant validity.Let’s say that while reading the manual you found that the BAI is highly correlated with the Hamilton Rating Scale (HRS) and the State Trait Anxiety Inventory (STAI), which are two previously validated measures of anxiety. This establishes convergent validity.
Convergent validity is the degree to which a measurement agrees with other measurements that assess the same construct.You also found that the BAI has a low correlation with the Beck Depression Inventory, which is meant to measure depression. This establishes discriminant validity. Discriminant validity is the degree to which a measurement does not correlate with other measurements that assess different concepts, so that it differentiates between the two constructs.
You also read in the manual that the BAI items were selected based on their similarity to the criteria for anxiety disorders as given in the Diagnostic and Statistical Manual of Mental Disorders. Furthermore, the items cover the entire range of anxiety symptoms, including those found in panic and generalized anxiety disorders. This establishes the content validity of the BAI. A measurement has content validity when its items cover all aspects of the construct being measured. In other words, content validity lets us know if the items on the BAI adequately cover all areas of anxiety.
Criterion-related validity refers to the degree to which a measurement can accurately predict specific criterion variables. Concurrent validity and predictive validity are the two types of criterion-related validity. Concurrent validity involves measurements that are administered at the same time, while predictive validity involves one measurement predicting future performance on another.Say that you found a significant correlation between the scores on the BAI and the scores on the HRS and STAI. You have established concurrent validity, which is the degree in which the scores on a measurement correspond to other measurements that have already been established as valid.If the scores on the BAI are significantly correlated with people who are diagnosed with an anxiety disorder in the future, the BAI has predictive validity. Predictive validity is the degree to which the scores on the measurement being evaluated correspond to another criterion measurement that is taken at a future date.
In our example, the anxiety diagnosis (criterion measurement) comes after the administration of the BAI (the test being evaluated).
Why Is Validity Important?
Let’s assume that you found out weeks after you administered the BAI to your client that the BAI did not measure anxiety as it was supposed to. What does this mean for your client? This means that the interpretations of the BAI results that you made related to your client’s level of anxiety were not valid. As a result, any inferences that you drew based on the test would not be accurate. For example, if you diagnosed your client with anxiety based on the BAI results, your diagnosis would be wrong since the test was not measuring anxiety.The treatment interventions you implemented would probably be ineffective since your client does not actually have anxiety.
If you decided to help your client get anti-anxiety medications, you would find that the medications are not helping or making your client worse. You can see here why validity is important in psychology. Without validity, your assessment results are completely useless, and your attempts to help the client using the information from the assessment could end up harming your client.
Let’s review. Validity refers to the extent to which a test measures what it is supposed to measure. There are three types of validity. Construct validity, which is the degree to which a test measures the construct that it is supposed to measure.
The two necessary components of construct validity are convergent and discriminant validity. Content validity refers to whether the items on a measurement represent all aspects of the construct being measured.Criterion-related validity refers to the degree to which a measurement can accurately predict specific criterion variables. Concurrent validity and predictive validity are the two types of criterion-related validity.
In order for a test to be valid, it needs to have construct validity, content validity, and criterion-related validity. So, the next time someone comes in your office for an assessment, don’t forget to pull out the test manual and look for evidence of validity.
By watching this lesson and increasing your knowledge of validity in psychology, you could subsequently go on to:
- Describe validity with regards to testing and psychology
- Contrast construct validity and content validity
- Determine what criterion-related validity refers to
- Understand the importance of validity