Question

Concepts of convergent evidence for validity, discriminant evidence for validity, test content validity and face validity for designing a psychological test to measure happiness.

Answer 1

ANS-  

When people talk about psychological tests, they often ask whether the test is valid or not. What exactly does this mean? Validity is a measure of how well a test measures what it claims to measure.

Psychological assessment is an important part of both experimental research and clinical treatment. One of the greatest concerns when creating a psychological test is whether or not it actually measures what we think it is measuring.

Convergent Validity and Discriminant Validity - Convergent Validity is a sub-type of construct validity. Construct validity means that a test designed to measure a particular construct (i.e. intelligence) is actually measuring that construct. Convergent validity takes two measures that are supposed to be measuring the same construct and shows that they are related. Conversely, discriminant validity shows that two measures that are not supposed to be related are in fact, unrelated. Both types of validity are a requirement for excellent construct validity.

Example :

Let’s say you were researching depression in college students. In order to measure depression (the construct), you use two measurements: a survey and participant observation. If the scores from your two measurements are close enough (i.e. they converge), this demonstrates that they are measuring the same construct. If they don’t converge, this could indicate they are measuring different constructs (for example, anger and depression or self-worth and depression).

Defining constructs can be a challenge. Therefore, applying convergent validity and discriminant validity can also be a challenge. Convergent validity is usually accomplished by demonstrating a correlation between the two measures, although it’s rare that any two measures will be perfectly convergent. In the case of discriminant validity, you could show that there is no correlation at all.

Correlation is measured by a correlation coefficient, r, on a scale of -1 to 1, where r=-1 is perfect negative correlation, r=1 is perfect positive correlation, and r=0 is no correlation at all. Convergent validity is sometimes claimed if the correlation coefficient is above .50, although it’s usually recommended at above .70.

Content Validity - When you create a test or questionnaire for a particular subject, you want the questions to actually measure what you want them to. For example, the AP Physics exam should cover all topics actually taught to students and not unrelated material like English or biology. This matching between test questions and the content the questions are supposed to measure is called content validity. If some of the test questions are measuring something else, this can create bias.

Example:

More formally, that “something” you are trying to measure is called a construct. A construct can be (almost) anything. Simple constructs include height, weight and IQ. More complicated constructs include: ability to perform well at a certain job; competency with wide-ranging subject areas like physics or U.S. history, and ability to evaluate other people’s psychiatric condition.

Face Validity : Content validity is also similar to face validity. However, they both use different approaches to check for validity. Face validity is an informal way to check for validity; anyone could take a test at it’s “face value” and say it looks good. Content validity uses a more formal, statistics-based approach, usually with experts in the field. These experts judge the questions on how well they cover the material.

Content validity and internal consistency are similar, but they are not the same thing. Content validity is how well an instrument (i.e. a test or questionnaire) measures a theoretical construct. Internal consistency measures how well some test items or questions measure particular characteristics or variables in the model. For example, you might have a ten-question customer satisfaction survey with three questions that test for “overall satisfaction with phone service.” Testing those three questions for satisfaction with phone service is an example of checking for internal consistency; taking the whole survey and making sure it measures “customer satisfaction” would be an example of content validity.