Types of Variable

Types of Variables in Psychology Research

In experimental scientific research, the researcher's goal is to provide evidence supporting a phenomenon regarding whether it exists or doesn't exist.

Psychology research has three variables: independent (IV), dependent (DV), and extraneous variables. Let us take a look at the definition of each variable.

The IV is what the researcher proposes as the cause of a phenomenon. Thus, by manipulating changes in the IV, the researcher can establish if the changes affect the DV.

The researcher doesn't always have to manipulate the IV. Sometimes it can be naturally occurring. A researcher can't manipulate the sun, but it can measure how exposed the subject is to sunshine.

Fig 1. - An example of a naturally occurring IV is the amount of homework done each day.

Now let's move on to understand what the DV is.

The DV is what the researcher expects to be the outcome/ changes that occur due to manipulating the IV; therefore, it is considered the effect.

In experimental research, cause-and-effect can be determined as the researcher measures the IV and DV whilst controlling external influences.

Psychological Variables Examples

To help us understand the concept of IVs and DVs, let us take a look at some examples.

Each example describes a hypothetical hypothesis and then identifies the IV and DV of the study.

In this research design, the researchers may compare sleep-deprived versus non-sleep-deprived students' test scores.

You can probably see the pattern, but in this study, the researchers may explore how long it took for babies to fall asleep who were listening to piano music versus those who were not.

Extraneous Variables in Research

Extraneous variables are variables that could unknowingly affect the dependent variable. In an experiment, the independent variable should be the only thing that affects the dependent variable. However, sometimes there may be other 'nuisance' variables that actually affect the dependent variable.

A theoretical experiment investigated the effect of the IV; whether children received Kumon lessons or not on the DV; end-of-year-grades.' If the study found that children who received Kumon lessons received better grades than those who did not, the researcher can infer that Kumon may boost academic performance.

However, there may be other variables we didn't consider that affected the dependent variable.

These other variables that could affect the dependent variable are called extraneous variables.

Types of Extraneous Variables in Psychology

There are two basic types of extraneous variables: participant and situational variables.

Let's look at both in more detail.

Situational Variables: Psychology

Situational variables are factors in the environment that could affect participants' performance. Some examples of these are the temperature of the room and the noise in the room.

In our example experiment, music would be a situational variable and academic performance a participant variable.

An example of how researchers can control situational variables is:

• Standardisation is when the experiment procedure is the same for each participant, So all participants experience the same things when they undergo the study.

The presence of situational variables reduces the validity of the experiment.

Fig 2. - Music is an example of a situational variable.

Participant Variables: Psychology

Participant variables are individual traits of a participant that could affect their performance in the experiment. Some examples of these are gender, age, intelligence and socioeconomic status.

There are a few different ways to reduce extraneous variables, these are:

• Random allocation: this is exactly what the name implies. Participants are randomly allocated to a group instead of the experimenter assigning participants to groups.

• Single or double-blind technique: a single-blind technique is when participants don't know what the experimental conditions are; this way, they won't behave in a way they think the experimenters would want and bias the results.

When looking at studies, there will usually always be some extraneous variable you can find. Recognising these extraneous variables will give you an edge in critically analysing studies, leading to extra marks in evaluation.

Confounding Variables in Psychology Research

A confounding variable is an extraneous variable related to the independent and dependent variables. I.e., a confounding variable is correlated with the independent variable and has a direct effect on the dependent variable.

A high standard of research is ensured by taking into account confounding variables. In this way, researchers can be reasonably confident that the independent variable is the only thing affecting the dependent variable.

Some ways to reduce confounding variables are:

• Restriction: only recruiting participants with similar characteristics or qualities, such as only using females age 30 for a study.

• Matching participants: in this method, one participant is matched with another, and these pairs are split into two groups. And only one of the groups experiences the IV, and the other doesn't.

• Randomisation: in this method, the researcher randomly allocates participants to each group. In this way, any confounding factors should be evenly distributed between the groups, thus not affecting the independent and dependent variables.