Quasi-experimental research: what is it and how is it designed?

What are the characteristics of quasi-experimental research and how is it used?

Quasi-experimental research is a type of research widely used in psychology.. Its most relevant characteristic is that the experimental groups are not randomly selected, but rather already formed groups are chosen (for example, a soccer team).

It is based on a descriptive methodology and on some quantitative and qualitative elements, and it is used to study different behaviors, social variables, etc. In this article we will learn about its characteristics and some differences with experimental research, as well as the advantages and disadvantages it presents.

What is quasi-experimental research?

Quasi-experimental research is used especially in the field of psychology, but also in the social sciences. It consists of a type of research halfway between experimental research and observational research.. In fact, many authors do not consider it to be scientific, although it has significant advantages, as we shall see in this article.

In contrast to experimental research, in quasi-experimental research the degree of control of extraneous variables (VVEE) is lower.. Extraneous variables are those variables or factors that produce an effect on the variable we are studying (dependent variable), but which we must control, since their effect is different from that produced by the independent variable(s) (which are the ones we are interested in studying).

How do we do research?

But how do you actually do research? In quasi-experimental research as well as in other types of research, whether in psychology or in other sciences, the research is mainly based on studying the effect of an independent variable (IV) (or more) on another variable, called the dependent variable (DV) (or more).called dependent variable (DV) (or more).

For example, we do research when we want to study the efficacy of a treatment (independent variable) in reducing anxiety (dependent variable).

Origin

Quasi-experimental research has its origins in the educational field. It arose from the observation that some effects or phenomena could not be studied using the experimental method, and alternative designs had to be used. These were mainly social phenomena or variables.

In recent years, the number of studies carried out through quasi-experimental research has been increasing.

Characteristics

There are certain characteristics that differentiate quasi-experimental research from other types of research. They are the following.

Non-randomness

The basic characteristic of quasi-experimental research (and which differentiates it from properly experimental research) is non-randomness in the formation of the experimental groups.. That is, the researcher selects already formed groups (for example, students in a course or workers in an office) to carry out his experiment.

In addition, this type of research is used subjects cannot be randomly assigned to the different experimental conditions of the investigation. conditions of the investigation.

Example

To illustrate this, let us consider an example: let us imagine that we want to study the efficacy of three types of psychological therapy (e.g. psychodynamic, cognitive-behavioral and systemic) in reducing the level of anxiety in a group of people.

If we were to use an experimental and not a quasi-experimental design, we would assign the subjects to the different experimental conditions (in this case, the three types of therapy) randomly, i.e., using chance.

In quasi-experimental research, on the other hand, we would not be able to do this. To overcome this problem, often a control group is included in the experiment..

2. No control of secondary systematic variance

On the other hand, quasi-experimental research is also a good option when secondary systematic variance cannot be controlled.The secondary systematic variance arises when the internal validity of the experiment is threatened. Internal validity is that which ensures that the independent variable is the cause of the dependent variable (i.e., exerts an effect on it).

Implications

When a quasi-experimental type of research is used, and since the experimental groups are not randomly selected, one thing happens: we cannot guarantee that all subjects will have the same effect. we cannot guarantee that all subjects will have similar characteristics.. In other words, there is less control of the variables. This makes the results less reliable (hence the name "quasi-experimental").

This means that this type of research is not so much used in laboratory contexts, but rather in natural contexts.but rather in natural contexts, in schools, etc. In other words, it is mainly used in applied research.

Thus, quasi-experimental research has both positive and negative components. Let's take a look at their advantages and disadvantages.

Advantages

The main advantage of quasi-experimental research is that it it allows the selection of accessible and already formed groupsIn addition, it is often difficult to find groups that meet all the requirements to participate in an experiment (as would be the case in an experimental design).

On the other hand, these designs are easy to apply and inexpensive. The preparation time and resources required are less than in an experimental design. In addition, it is a type of research that can be applied not only to study groups, but also individual cases.

Disadvantages

As negative characteristics or disadvantages in quasi-experimental research, we find its lower precision and lower validity, compared to experimental designs..

In addition, the lack of randomization in the formation of the groups poses a threat to the validity of the experiment and the precision or accuracy of the experiment.

On the other hand, often in this type of experiment, the so-called placebo effect is produced, which consists of feeling or perceiving an improvement after believing that we havewhich consists of feeling or perceiving an improvement after believing that we have received a treatment (which in reality we have not received).

Types of designs

In quasi-experimental research, specifically in the field of psychology, two types of quasi-experimental designs are used in particular:

1. Cross-sectional designs.

From these designs different groups are studied at a specific point in time. For example, we can use them to measure the intelligence quotient (IQ) of a class of 4th grade of ESO on January 1st .

In other words, this type of design is based on collecting data at a specific moment in time (at a single point in time). The objective is to describe and analyze a series of variables.

2. Longitudinal designs

This second type of design, the longitudinal, study how certain variables (or a single variable) evolve or change in a group of subjects (or more).. In other words, they study these variables at different points in time. For example, in January, February and March (although it could be with time intervals of years, also, or more).

They can also be applied individually for single cases. The objective is to study the change that occurs in "X" period of time.