Psychological tests: characteristics and operation

Psychological tests or tests are the tools that psychologists use to measure those variables that they are interested in knowing. Just as a scale is used to measure weight, in psychology we have instruments that allow us to know some parameters about anxiety, emotions and personality, among others. Now, these tests are only useful if they meet quality standards.

So, Every measuring instrument is based on the formula X=V+E. Where X represents the measurement given by the test, which is the sum of V, the real score, plus E, the measurement error. This simple equation shows us a way to investigate the quality of psychological tests. And through it, we can build instruments where X and V are as similar as possible in all subjects. On the other hand, it is important to mention that the study of how to measure psychological constructs is called psychometrics.

However, What should we do to build a good instrument? What indicators do we have to know if psychological tests are good or bad? To answer these questions, we are going to talk about the aspects to take into account when making a good instrument. In addition, we will also explain the concepts of validity and reliability, which will show us the quality of the test. Let’s dig deeper.

How to build psychological tests?

Building a test is a laborious process that takes many hours of work and research. As a prior step to the construction process, three essential questions must be answered:

What do we want to measure with it?Who do we want to measure?What are we going to use it for?

The first question allows us to know the variable under study. It seems trivial to clearly define what we want to measure, but if not done correctly, it can lead to great confusion. A historical example of this occurred with intelligence: different instruments began to be made to measure it but no one defined it. We are still suffering the consequences of this, having a multitude of disparate definitions of the intelligence construct and various tests that measure different things.

A key aspect when defining a construct to measure is knowing what we measure it through. Psychological constructs cannot be observed directly (see, for example, anxiety), but we can measure them through the behaviors they generate. Therefore, it is necessary to explain the behaviors by which the variable under study is manifested.

The second question is useful for us to adapt the test to the population we want to measure. Obviously, we cannot do psychological tests that are valid for all ages and conditions. Therefore, It is essential to know what the target population is like and adapt the instrument to the needs and qualities of the subjects.

Every test is built with an objective and can even be multiple, such as diagnosing a disorder, selecting subjects, conducting research, etc. The third question helps us focus the instrument towards its usefulness. Even if two tests seek to measure the same thing, they can differ greatly if their objective is different. For example, if what we are looking for is to measure intelligence, it will not be the same test if we want to detect gifted children as if we want to detect deficiencies.

Thus, the answers to these three questions are the foundations of any psychological test. An in-depth study of them will be essential if we seek to build a valid and reliable instrument.

The quality of psychological tests

In psychometrics, when measuring whether a test fulfills its function, there are two fundamental indicators. These indicators are validity and reliability. Throughout history, a multitude of statistical formulas have been designed to calculate them and prove the quality of the tests. But what are validity and reliability?

Validity of a test

When we talk about the validity of a test, we are referring to the ability of that test to measure what it wants to measure. That is, if we want to measure the degree of anxiety in a person, the test will be valid if it measures anxiety and only anxiety. It may seem to a certain extent absurd that a test measures something that we do not want, but when the construct is poorly defined it is possible that the design of the instrument results in very low validity.

To measure the validity of a test there are several statistical resources. The most common are the correlation of the test we want to measure with another, whose validity has already been previously verified, and evaluate it through different expert judges and see to what extent these judges agree.

Reliability of a test

The degree of reliability is the scale that indicates the precision that a test has when measuring. That is, a test will be reliable when we give the same instrument twice to the same person and obtain the same result. If every time we pass the test, the result is different, this would mean that the measurement error would be so high that it distorts the results. It is as if every time we put the same object on a scale it gave a different weight.

There are also different statistical strategies to measure reliability, but the best known is to give the same test twice to a group of people and see the correlation between the first and the second measurement. A high correlation would show us high reliability and that the test fulfills its function.

Finally, mention that psychological tests are used in all branches of psychology, from the most applied to research. Therefore, it is essential that its construction is fully controlled so that the results are valid and reliable.

You might be interested…