In this lesson, we will learn all about the construct validity. Explore the difference between convergent and discriminant validity, the threats to construct validity, and more.
Looking for Construct Validity
Imagine that you are a psychologist, and your client has been reporting feeling fatigued and hopeless as well as loss of appetite. These symptoms fit the definition of depression, but you can’t determine the severity of your client’s depression just by hearing the symptoms.
You look around your office for a tool that can measure your client’s level of depression. You find a Beck Depression Inventory (BDI) and come across evidence that shows the BDI is a psychological assessment that accurately measures depression. In this example, the BDI has construct validity. That is, the BDI is able to measure depression, which is the construct you want to measure.
What is a Construct?
Intelligence, motivation, anxiety, and fear are all examples of constructs.
In psychology, a construct is a skill, attribute, or ability that is based on one or more established theories. Constructs exist in the human brain and are not directly observable. For example, though you may know a person is smart by the way they speak and what they say, you cannot directly observe intelligence.
You can tell someone is anxious if they are trembling, sweating, and restless, but you cannot directly observe anxiety. You also cannot directly observe fear or motivation. They are all complex, abstract concepts that are indirectly observed through a collection of related events.
What is Construct Validity?
Construct validity refers to how well a test or tool measures the construct that it was designed to measure. In other words, to what extent is the BDI measuring depression? There are two types of construct validity: convergent and discriminant validity. Construct validity is established by looking at numerous studies that use the test being evaluated.Imagine that you wanted to evaluate the construct validity of the BDI. You could perform a differential-groups study by comparing the BDI scores for people who have depression (the construct) to the scores of people who do not have depression.
If the group that has depression scores higher on the BDI than the group without depression, this is proof of the construct validity.Let’s say that you had a group of people take both the BDI and the Hamilton Psychiatric Rating Scale for Depression, a previously validated measure of depression. You found that the two tests were highly correlated.
This establishes convergent validity, which is how well a test agrees with other previously validated tests that measure the same construct.Assume that you also had that same group of people take the Hamilton Psychiatric Rating Scale for Anxiety, which is a previously validated test that measures anxiety. You found a low correlation with the Hamilton Rating Scale for Anxiety and the BDI. This establishes discriminant validity, which is the extent to which a test measures what it is supposed to and not some theoretically unrelated construct. Discriminant validity is also referred to as divergent validity.
Threats to Construct Validity
There are several things that can interfere with construct validity. One such issue is not having a solid definition of the construct. For example, Internet addiction is a relatively new illness, and psychologists are still working on ways to define it.Another potential problem is not conducting enough research studies to prove construct validity. Construct validity cannot be based off one research study alone.
A single study can be biased, or it can lead you to draw incorrect conclusions. The more research studies you have that support construct validity, the more likely it is that your test is actually measuring the construct it is supposed to measure.Researchers may also find that they lose connection between the theoretical construct and how it is experienced in the real world. Let’s say you created a test that uses the amount of times a person cries as a measure of depression. You know that not everyone who experiences depression cries. You also know that there are other reasons for people to cry, i.
e., when they hurt themselves or when they have something in their eyes. Crying is not the typical way in which people experience depression in the real world. Depression involves a combination of symptoms.Another common pitfall is having administration and scoring procedures that interfere with the outcomes of the test. Let’s say that you administer your test in a cold, gray room with little sunlight. The atmosphere of the room can put your study participants in a bad mood which, in turn, would affect their responses.
Finally, the expectations of the experimenter can influence the outcomes of a study, consciously or unconsciously. For example, the researcher can communicate the desired outcome to the participants by looking happy when the participants respond in the way the experimenter expects them to. Participants that want to make themselves look good may pick up on this and modify their responses to please the experimenter.
Let’s review. Construct validity refers to how well a test or tool measures the construct that it was designed to measure. Discriminant validity and convergent validity are the two components of construct validity.
There are several threats to construct validity. These include poor item analysis and an inadequate definition of the construct. So, before you decide to give a psychological assessment to your client, remember to ask yourself how well a test measures the construct that it claims to measure.
Ponder the details of this lesson, then test your ability to:
- Recognize the function of a BDI
- Indicate knowledge of the meaning of construct viability
- Identify the two types of construct validity
- Discuss some of the threats to construct viability